Revelation 13:18

18Hereὧδεtheἡwisdomσοφίαisἐστίν·The [one]ὁhavingἔχωνunderstandingνοῦνlet him countψηφισάτωtheτὸνnumberἀριθμὸνof theτοῦbeastθηρίου,numberἀριθμὸςforγὰρa man’sἀνθρώπουit isἐστίν·andκαὶtheὁnumber [is]ἀριθμὸςof itαὐτοῦsix hundredἑξακόσιοιsixtyἑξήκονταsixἕξ.

Here is the wisdom. The one having understanding, let him count the number of the beast, for it is a man’s number, and its number [is] six hundred sixty-six.