From the NET footnotes:

55 tc A few MSS (𝔓115 C, along with a few MSS known to Irenaeus {and two minuscule MSS, 5 and 11, no longer extant}), read 616 here, and several other witnesses have other variations. Irenaeus’ mention of MSS that have 616 is balanced by his rejection of such witnesses in this case. As intriguing as the reading 616 is (since the conversion of Nero Caesar’s name in Latin by way of gematria would come out to 616), it must remain suspect because such a reading seems motivated in that it conforms more neatly to Nero’s gematria.

The Greek gematria value of Nero Caesar (Νέρων Καῖσαρ) would be 1,005, but the Grecized Hebrew (נרון קסר‬) value equates to 666 as indicated above. Metzger elaborates:

When Greek letters are used as numerals the difference between 666 and 616 is merely a change from ξ to ι (666 = χξς and 616 = χις). Perhaps the change was intentional, seeing that the Greek form Nero Caesar written in Hebrew characters (‮נרון קסר‬) is equivalent to 666, whereas the Latinized Hebrew form Nero Caesar (‮נרו קסר‬) is equivalent to 616.¹

Given the few variant MSS and the fact that the discrepancy conforms to the Latin form of the most likely referent (by simply removing the ן), it is highly probable that 666 was the original number (as most modern translations render this passage).

_{¹ Bruce Manning Metzger, United Bible Societies, A Textual Commentary on the Greek New Testament, Second Edition (A Companion Volume to the United Bible Societies’ Greek New Testament, 4th Rev. Ed.) (London; New York: United Bible Societies, 1994), 676.}

From the NET footnotes:

55 tc A few MSS (𝔓115 C, along with a few MSS known to Irenaeus {and two minuscule MSS, 5 and 11, no longer extant}), read 616 here, and several other witnesses have other variations. Irenaeus’ mention of MSS that have 616 is balanced by his rejection of such witnesses in this case. As intriguing as the reading 616 is (since the conversion of Nero Caesar’s name in Latin by way of gematria would come out to 616), it must remain suspect because such a reading seems motivated in that it conforms more neatly to Nero’s gematria.

The Greek gematria value of Nero Caesar (Νέρων Καῖσαρ) would be 1,005, but the Grecized Hebrew (נרון קסר‬) value equates to 666 as indicated above. Metzger elaborates:

When Greek letters are used as numerals the difference between 666 and 616 is merely a change from ξ to ι (666 = χξς and 616 = χις). Perhaps the change was intentional, seeing that the Greek form Nero Caesar written in Hebrew characters (‮נרון קסר‬) is equivalent to 666, whereas the Latinized Hebrew form Nero Caesar (‮נרו קסר‬) is equivalent to 616.¹

But what of the other variants? It is true that MS 2344 has 665 and one old Latin text (codex ar, 9th century) even has 646, but these variant readings have so little support that they cannot even be considered alternatives to the 666 reading.

Given the few variant MSS and the fact that one of the earliest discrepancies conforms to the Latinized form of the most likely referent (by simply removing the ן), it is highly probable that 666 was the original number (as most modern translations render this passage).

_{¹ Bruce Manning Metzger, United Bible Societies, A Textual Commentary on the Greek New Testament, Second Edition (A Companion Volume to the United Bible Societies’ Greek New Testament, 4th Rev. Ed.) (London; New York: United Bible Societies, 1994), 676.}

From the NET footnotes:

55 tc A few MSS (𝔓115 C, along with a few MSS known to Irenaeus {and two minuscule MSS, 5 and 11, no longer extant}), read 616 here, and several other witnesses have other variations. Irenaeus’ mention of MSS that have 616 is balanced by his rejection of such witnesses in this case. As intriguing as the reading 616 is (since the conversion of Nero Caesar’s name in Latin by way of gematria would come out to 616), it must remain suspect because such a reading seems motivated in that it conforms more neatly to Nero’s gematria.

The Greek gematria value of Nero Caesar (Νέρων Καῖσαρ) would be 1,005, but the Grecized Hebrew (נרו קסר) value equates to 666 as indicated above. Metzger elaborates:

When Greek letters are used as numerals the difference between 666 and 616 is merely a change from ξ to ι (666 = χξς and 616 = χις). Perhaps the change was intentional, seeing that the Greek form Nero Caesar written in Hebrew characters (‮נרון קסר‬) is equivalent to 666, whereas the Latin form Nero Caesar (‮נרו קסר‬) is equivalent to 616.¹

Given the few variant MSS and the fact that the discrepancy conforms to the Latin form of the most likely referent, it is highly probable that 666 was the original number (as most modern translations render this passage).

_{¹ Bruce Manning Metzger, United Bible Societies, A Textual Commentary on the Greek New Testament, Second Edition (A Companion Volume to the United Bible Societies’ Greek New Testament, 4th Rev. Ed.) (London; New York: United Bible Societies, 1994), 676.}

From the NET footnotes:

55 tc A few MSS (𝔓115 C, along with a few MSS known to Irenaeus {and two minuscule MSS, 5 and 11, no longer extant}), read 616 here, and several other witnesses have other variations. Irenaeus’ mention of MSS that have 616 is balanced by his rejection of such witnesses in this case. As intriguing as the reading 616 is (since the conversion of Nero Caesar’s name in Latin by way of gematria would come out to 616), it must remain suspect because such a reading seems motivated in that it conforms more neatly to Nero’s gematria.

The Greek gematria value of Nero Caesar (Νέρων Καῖσαρ) would be 1,005, but the Grecized Hebrew (נרון קסר‬) value equates to 666 as indicated above. Metzger elaborates:

When Greek letters are used as numerals the difference between 666 and 616 is merely a change from ξ to ι (666 = χξς and 616 = χις). Perhaps the change was intentional, seeing that the Greek form Nero Caesar written in Hebrew characters (‮נרון קסר‬) is equivalent to 666, whereas the Latinized Hebrew form Nero Caesar (‮נרו קסר‬) is equivalent to 616.¹

Given the few variant MSS and the fact that the discrepancy conforms to the Latin form of the most likely referent (by simply removing the ן), it is highly probable that 666 was the original number (as most modern translations render this passage).

_{¹ Bruce Manning Metzger, United Bible Societies, A Textual Commentary on the Greek New Testament, Second Edition (A Companion Volume to the United Bible Societies’ Greek New Testament, 4th Rev. Ed.) (London; New York: United Bible Societies, 1994), 676.}