18 Here is wisdom: let him who has understanding, compute the number of the beast; for it is the number of a man; and its number is six hundred and sixty-six.
Revelation 13:18 Cross References - Living_Oracles
Mark 13:14
14 But when you shall see standing on forbidden ground, the desolating abomination, (reader, attend!) then let those in Judea flee to the mountains;
Romans 3:5
5 But if our unrighteousness display the justice of God, what shall we say? Is not God unjust, who inflicts vengeance? (I speak after the manner of men.)
Revelation 1:3
3 Happy is he that reads, and they that hear the words of this prophecy, and keep the things that are written in it; for the time is at hand.
Revelation 15:2
2 And I saw, as it were, a sea of glass mingled with fire; and those who overcame the beast, and its image, and its mark, and the number of its name; standing by the sea of glass, having the harps of God.
Revelation 17:9
9 Here is the mind that has wisdom. The seven heads are seven mountains, on which the woman sits.
Revelation 21:17
17 And he measured its wall, one hundred and forty-four cubits, according to the measure of a man, that is, of an angel.