I have read Making Sense of the Numbers of Genesis by Carol A. Hill as a brief overview of the symbolism of different numbers that appear in Genesis. But, I cannot start to make sense of the following passage about the beginning of the flood in Gen 7:11, NIV:

In the six hundredth year of Noah’s life, on the seventeenth day of the second month – on that day all the springs of the great deep burst forth, and the floodgates of the heavens were opened.

In a chapter from The Old Testament by Michael D. Coogan my lecturer shared with me, the documentary hypothesis is explained, and it is indicated that this particular verse is most likely to come from P. From what I understand about the different characteristics of the sources J, E, D and P it also seems that number symbolism fits best in the latter source (although this is not mentioned explicitly in the book).

I can understand that the 600 years are 10×60, but what about the 17th day of the 2nd month? The only thing I can think of is that if the first month had taken 30 days, that would add up to 47 = 40 + 7, both 'preferred numbers'.

  • This seems a little far-fetched, or doesn't it, compared to other examples of number symbolism?
  • If 30 + 17 = 47 = 40 + 7 were indeed the intended symbolism, what would be its meaning?
  • Was this, or other ideas concerning the number symbolism in this verse, discussed in scientific literature?

2 Answers 2


The number 17 seems to have had special significance, and figures prominently in the ages of the Patriarchs and many of the other ancestral characters in Genesis. For example:

  1. Abraham lived to 175 (5 X 5 X 7)
  2. Isaac lived to 180 (6 X 6 X 5)
  3. Jacob lived to 147 (7 X 7 X 3)


  • Each lifespan involves a perfect square (5, 6, then 7 in a numeric series),
  • the third factor also forms a series (7, 5, 3)
  • in each case the sum of the factors is 17.

Furthering the above formulas (3), Genesis says Abraham’s wife Sarah lived to 127 years, which is the sum of these consecutive square numbers plus 17

... and an equally improbable age. She also lived 17 years longer than Joseph, often referred to as the fourth Patriarch. As suggested by the question, the probability of Abraham, Isaac, Jacob and Sarah all living to exactly the ages to make this formula work is infinitesimal, even overlooking the great ages involved.

Other, simpler formulas based on the number 17 appear to exist for the ages of some pre-flood ancestors.

Leon R. Kass also points out in The Beginning of Wisdom: Reading Genesis Jacob spent his last 17 years in Egypt (Genesis 47:28). Joseph was sold into slavery at age 17 (Genesis 37:2).

In the Priestly contributions to the flood story, two important events occur on the seventeenth day of the month:

Genesis 7:11 (KJV): In the six hundredth year of Noah's life, in the second month, the seventeenth day of the month, the same day were all the fountains of the great deep broken up, and the windows of heaven were opened.

Genesis 8:4: And the ark rested in the seventh month, on the seventeenth day of the month, upon the mountains of Ararat.

With such evidence that the number 17 was in itself of numerological importance to the Priestly Source, I don't believe we need obscure symbolism to make sense of its use through 'preferred numbers'.

Noah was 500 when his first son was born, 600 when the flood came and 950 when he died: these are easy numbers for tradents to remember when passing traditions down orally. The number 40 is similarly an easy number to remember; we find multiples of 20 years commonly used for the major judges in the Book of Judges. Once again the simplest explanation is best. When we find number that are easy to remember being used in material dating back to the very earliest Israelite traditions, they were likely used for the reason that they were easy to remember.

  • Sorry, I don't follow your maths. How are 5, 6, and 7 "a perfect square"?
    – fdb
    Sep 5, 2015 at 23:12
  • 3
    @fdb "Each lifespan": Abraham's lifespan involves a perfect square (5X5); Isaac's lifespan involves a perfect square (6X6); Jacob's (7X7). Each perfect square is multiplied by a third factor (7, then 5, then 3) to give the patriarch's age when he died. Sep 6, 2015 at 5:24
  • 4
    Do you have evidence that the ancient Hebrews had any conception of square numbers?
    – fdb
    Sep 7, 2015 at 10:17
  • 1
    Your link is talking about the Hellenistic period (after Alexander). By the way, there are lots of good books about the history of mathematics, in case you want to delve into this matter.
    – fdb
    Sep 7, 2015 at 22:10
  • 1
    I am not sure 'most scholars' believe in the documentary hypothesis! Sep 8, 2015 at 7:57

Doing the Math

The initial significance is 17 was chosen by God as the day on which the rain would start; He then affirms the number by repeating it when the Ark is brought to rest on the same day:

And God said to Noah...For behold, I will bring a flood of waters upon the earth to destroy all flesh in which is the breath of life under heaven. Everything that is on the earth shall die. (Genesis 6:17) [ESV]

In the six hundredth year of Noah's life, in the second month, on the seventeenth day of the month, on that day all the fountains of the great deep burst forth, and the windows of the heavens were opened. (Genesis 7:11)

and in the seventh month, on the seventeenth day of the month, the ark came to rest on the mountains of Ararat. (Genesis 8:4)

The 17th day was chosen by God. Yet, once this is known, it brings insight to other details:

For in seven days I will send rain on the earth forty days and forty nights, and every living thing that I have made I will blot out from the face of the ground. (7:4)

If the rain started on the 17th, then the day God spoke to Noah was the 10th day of the month. If we presume a 30-day month,1 this is the picture of the beginning of the 600th year of Noah's life: enter image description here Forty days after the beginning of the year (on the 10th day of the 2nd month), God told Noah he had 7-days before 40-days of rain would start. The primary date is the first day of the year and there are three periods of time, two of 40-days and one of 7-days. In effect, God begins this year by waiting 40-days before telling Noah it is the time of judgment. Once the judgment is announced, Noah has 7-days to load the Ark before the 40-days of rain will start.

A 7-day period comes from creation and the new number of significance is 40 which is introduced as a number of judgment.2 The application of the 40-day period from the 1st day of the year determines the date of the announcement: the 10th day of the second month. (This also serves as an explanation to the question why the flood did not start in the first month of the year, like the Exodus.) Then there is a 7-day period before the flood begins on the 17th. Thus, while there are certainly future instances which reflect the significance of the number 17 (as shown in Dick Harfield’s answer),3 the immediate significance follows from simply “doing the math” using the explicitly stated periods and the logical starting point:

  • First day of the year
  • Forty days (of waiting) - the 10th day of the second month
  • Seven days - the 17th day of the second month
  • Forty days (of rain) - the 27th day of the third month

One might be tempted to say there is no intrinsic value to the number 17; it is simply a consequence of doing the math. However, these facts are only known because we are told the flood begins on the 17th and the Ark came to rest on the 17th. This same information could have been conveyed by stating the day of the announcement was the 10 day of the second month; so God’s choice in all of these numbers is to make 17 reveal other facts in the flood narrative:

  • The flood begins on the 17th day of the 2nd month, revealing God spoke to Noah on the 10th day of 2nd month
  • The Ark comes to rest on 17th day of the 7nd month, revealing God was using a calendar composed of 30-day months.
  • These two reveal the 10th day of the 2nd month was the 40th day of the in the 600th year of Noah’s life.

There is another aspect of revelation which comes from “doing the math.” Since the rain fell for 40-days, it stopped on the 27th day of the 3rd month, the same day of the month God will command Noah to leave the Ark:

In the second month, on the twenty-seventh day of the month, the earth had dried out. Then God said to Noah, “Go out from the ark... (8:14-16)

Thus repetition (17, 27, and 40) is also a part of the revelation.

God's Work and His Nature

The symmetry of the announcement, (40-days/7-days/40-days) is immediately paralleled on the calendar (17th day of the second month/150 days/17th day of the seventh month). The triad of elements has been arranged by putting the different one in-between the two alike:

 40-days of God waiting
    7-days of Noah acting
 40-days of rain (God acting)

 17th day of second month the Ark is "lifted up" from the earth
    150 days of the Ark upon the water [see note 4]
 17th day of seventh month the Ark "rests" on the earth   

In addition there is a "remembrance" triad implied in the second month of the second year before Noah leaves the Ark and hears God's covenant:

Second month of the second year:
10-days flood was announced (last year)
  7-days Noah "remembers" the seven days he to load the Ark (last year)
10-days Noah waits for God to announce His covenant (this year)
[27th day Noah leaves and God fulfills His promise to make a covenant]

The number 17 can be divided and arranged into 3 parts, 2 of which are alike (7) and 1 which is different (3). The first 7 is symbolic of creation; the second 7 is symbolic of the Sabbath. The remainder of 3 is symbolic of the triune nature of God:

7 Creation
  3 God: Father-Son-Spirit
7 Sabbath

Finally, since they were written later, it is common to consider the Hebrew Scriptures through the lens of dependency on earlier Sumerian writings:

One disadvantage of the Sumerian numbering system was ambiguity. The Sumerians wrote their system of numbers in cuneiform—a series of wedged marks impressed onto clay tablets. Although the Babylonians had developed the important principle of “position” (place-value notation) in writing numbers, the absolute value of the digits impressed on cuneiform tablets remained a matter of intelligent guesswork. Another uncertainty was introduced through the fact that a blank space in a cuneiform text could sometimes mean zero (the Mesopotamians had no symbol for zero). In practice, these types of ambiguities were not that serious for Mesopotamian scribes because the order of magnitude and position of the numbers could be realized from the context of the tablet (e.g., whether one was denoting rations of barley, rings of silver, or whatever). However, such contextual ambiguities could have created confusion for later Hebrew biblical scribes who were not familiar with the sexagesimal system and its peculiarities.5

The use of numbers in the flood narratives demonstrates the Hebrew writer was aware of the sexagesimal system. In fact 30-day months and a 360-day year are essential elements to the narrative. Yet the role is revealed indirectly by using the numbers 17 and 150 (which have no place in a sexagesimal system). Even then the reference is muted as it speaks to five months and locates God speaking to Noah on the 40th day of the year. In other words the writer uses, but never directly acknowledges the sexagesimal system.

Thus the number 17 not only reveals God’s work and His nature, it is used to demonstrate knowledge of the Mesopotamian sexagesimal system without directly acknowledging it or accepting the symbolic meaning of 60 (or any of its multiples). This speaks to the originality and authenticity of the Hebrew account.

1. The number of days before the Ark came to rest is 150 (7:24, 8:3), and it came to rest on the 17th day of the 7th month. The total time was both 150-days and 5-months. Therefore a month is 30-days and a year is 12 months and 360-days.
2. Carol A. Hill identifies 40 as one of the Bible’s Preferred or Figurative numbers. In addition to the two 40-day periods at the start of the flood (one implied and one directly stated), Noah waits 40-days before opening the window (8:6). There are several other instances where 40-days is found in the context of testing or judgment.
3. Additional instances of the number 17 in the Patriarchal history: Serug, the 17th generation was born in the year 1819 (107x17); Noah died in 2006 (118x17); Jacob was born in 2108 (124x17) [which leads to another use since 107 + 17 = 124].
4. The 150-day period is itself a triad: 50-50-50. The first 50-days are marked by rain and increasing waters; the second 50-days by waters covering; the third 50-days by receding waters.
5. Carol A. Hill, "Making Sense of the Numbers of Genesis", Perspectives on Science and Christian Faith, Dec 2003, p. 241

  • Your answer stands quite well without the appeal to the idea of earlier Sumerian writings, which seems somewhat dubious.
    – David
    Sep 14, 2020 at 20:26