It was brought to my attention that the original Greek says that "....for the number is that of a man", should actually read "....for the number is that of man". This infers that the "number" is tied to "a system created by man" (I'm still trying to get clarification as to what "that system is"). I sure wish I could read Greek or even Aramaic to find out if this is true.
Koine Greek does not have an indefinite article, and the definite article is not used the way the english definite article is used. That means it's up to the interpreter to add in indefinite articles as needed based on the context. Moreover the genitive can be translated with an apostrophe or the more ambiguous "of" construction. Finally anthropous can be "man" or "mankind". Therefore all of the following are legitimate literal translations:
- "for the number is that of a man"
- "for the number is that of man"
- "for that is man's number"
- "for that is mankind's number"
- "for the number is that of mankind"
Unfortunately you'll need more than a close reading of the Greek to distinguish among these -- some interpretation is required and different Bible translations will choose different variants based on their own interpretive tradition. Anyone who tells you it is clearly one of these and not the other is not telling you the whole story; they may well be right, but not because of the grammar of this clause.
(This should be a comment, but I'm new and don't have enough reputation points to comment) The above answer by user33515 doesn't seem to address the poster's question. The question is whether ἀνθρώπου should be translated into English with the indefinite article, "of a man", or without the indefinite article, "of man". The former (presumably) implies the Greek passage refers to a particular man while the latter (presumably) implies the Greek passage refers to mankind in general.
(As someone who doesn't know Koine Greek, the question seems to arise because there is no article in the Greek passage: ἀριθμὸς γὰρ ἀνθρώπου ἐστίν. Is there a rule in Greek grammar that determines whether a noun is concrete or abstract (collective?) based on the presence or absence of the article?)
I think the second part of the poster's question is meant to account for their interest in the matter. The poster is saying that if the English translation should omit the article, then they are inclined to believe that "mankind" refers to some system created by mankind.
All manuscripts of the Greek text read ἀριθμὸς γὰρ ἀνθρώπου ἐστίν. Translating literally in Greek word order yields the nonsensical, "Number for of a man it is". It is rendered in English word order as "for it is the number of a man" (e.g. NIV, ESV, KJV), "for the number is that of a man" (e.g. NASB), and even "because it is a human total number" (ISV).
The understanding in any event is that the number represents a man. There is a good discussion of how this number could "represent" a man here:
This rendering makes much more sense I.e. "mankind" or "human". It is not a mystical number. 666 is the number of years from the desecration of the temple by the Babylonians IN 596 BC, the first beast, and the desecration of the temple by the Romans, the second beast with all the authority over the Jews of the first beast, in 70 AD. John, in exile in a penal colony on the island of Patmos for sedition, was writing in code "which requires wisdom" to interpret, calling on the seven churches to rise up against Rome and restore Jerusalem and the Temple. To evade the attention of Roman prison warders reading his letter, he cries out "Babylon the great has fallen" and "i saw the new Jerusalam coming down from heaven", Babylon being code for Rome and 666, a human number being the clue.