A.T. Robertson Commentary Revelation 13:18

"Here is wisdom. He that hath understanding, let him count the number of the beast; for it is the number of a man: and his number is Six hundred and sixty and six." — Revelation 13:18 (ASV)

Here is wisdom (ωδε η σοφια). The puzzle that follows as in 17:9. See Eph 1:17 for "a spirit of wisdom and of understanding."

He that understands (ο εχων νουν). "The one having intelligence" in such matters. Cf. the adverb νουνεχως (discreetly) in Mr 12:34.

Let him count (ψηφισατω). First active imperative of ψηφιζω, old verb (from ψηφος pebble), to count, in N.T. only here and Lu 14:28.

The number of a man (αριθμος ανθρωπου). "A man's number." But what man and what name?

Six hundred and sixty-six (εξακοσιο εξηκοντα εξ). Unfortunately some MSS. here read 616 instead of 666. All sorts of solutions are offered for this conundrum. Charles is satisfied with the Hebrew letters for Nero Caesar, which give 666, and with the Latin form of Nero (without the final n), which makes 616. Surely this is ingenious and it may be correct. But who can really tell?