The number of the beast is associated with the Beast of Revelation in chapter 13, verse 18 of Book of Revelation. In most manuscripts of the New Testament and in English translations of the Bible, the number of the beast is six hundred and sixty-six. The papyrus 115 (which is the oldest preserved manuscript of the Revelation as of 2017), as well as other ancient sources like Codex Ephraemi Rescriptus, give the number of the beast as 616, NOT 666.
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Abp. Eric Michel