There are various different forms of the famous passage.
The Bible:
This calls for wisdom. If anyone has insight let him calculate the number of the beast, for it is man's number. His number is 666.
Iron Maiden:
Woe to you, Oh Earth and Sea, for the Devil sends the
beast with wrath, because he knows the time is short...
Let him who hath understanding reckon the number of the
beast for it is a human number, its number is Six hundred and
sixty six.
The Omen:
"Here is wisdom. Let him who has understanding calculate the number of the beast, for it is the number of a man; his number is 666.” (Book of Revelations, Chapter 13 : Verse 18)