http://www.americanvision.org/articlearchive/05-10-05.asp
Ancient numbering systems used an alpha-numeric method. This is true of the Latin (Roman) system that is still common today: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Greek and Hebrew follow a similar method where each letter of their alphabets represents a number. The first nine letters represent 1–9.3 The tenth letter represents 10, with the nineteenth letter representing 100 and so on. Since the Book of Revelation is written in a Hebrew context by a Jew with numerous allusions to the Old Testament, we should expect the solution to deciphering the meaning of six hundred and sixty-six to be Hebraic. "The reason clearly is that, while [John] writes in Greek, he thinks in Hebrew, and the thought has naturally affected the vehicle of expression."
When Nero Caesar's name is transliterated into Hebrew, which a first-century Jew would probably have done, he would have gotten Neron Kesar or simply nrwn qsr, since Hebrew has no letters to represent vowels. “It has been documented by archaeological finds that a first century Hebrew spelling of Nero's name provides us with precisely the value of 666. Jastrow's lexicon of the Talmud contains this very spelling.
When we take the letters of Nero's name and spell them in Hebrew, we get the following numeric values: n=50, r=200, w=6, n=50, q=100, s=60, r=200 = 666. “Every Jewish reader, of course, saw that the Beast was a symbol of Nero. And both Jews and Christians regarded Nero as also having close affinities with the serpent or dragon. . . . The Apostle writing as a Hebrew, was evidently thinking as a Hebrew. . . . Accordingly, the Jewish Christian would have tried the name as he thought of the name—that is in Hebrew letters. And the moment that he did this the secret stood revealed. No Jew ever thought of Nero except as ‘Neron Kesar.
A fragment from the oldest surviving copy of the New Testament shows that the number of the Beast of Revelation 13 is 616. Ellen Aitken, a professor of early Christian history at McGill University, states that “the majority opinion seems to be that it refers to [the Roman emperor] Nero.” The early fragment supports the view that Revelation was written prior to the destruction of Jerusalem in A.D. 70, and whether the number is 666 or 616, the number is a reference to Nero and not some end-time antichrist figure.
The fragment supports the reading of some Greek New Testament manuscripts that read 616 instead of 666. Why would someone making a copy of the Revelation scroll make such a number change? “Perhaps the change was intentional, seeing that the Greek form Neron Caesar written in Hebrew characters (nrwn qsr) is equivalent to 666, whereas the Latin form Nero Caesar (nrw qsr) is equivalent to 616.” A Latin copyist might have thought that 666 was an error because Nero Caesar did not add up to 666 when transliterated into Latin. He then changed 666 to 616 to conform to the Latin rendering since it was generally accepted that Nero was the Beast. In either case, a Hebrew transliteration nets 666, while a Latin spelling nets 616. Nero was the “man” and either 666 or 616 was his number.