The number of the Beast (from Ancient Greek: ἑξακόσιοι ἑξήκοντα ἕξ, romanized: hexakósioi hexēkonta héx, lit. 'six hundred sixty-six') is the fear of the number 666. It comes from the Biblical verse Revelation 13:18, which says that the number 666 is the number of the beast, associated with Satan or the Antichrist.
A well-known example of this fear is Nancy and Ronald Reagan, who, in 1989, when moving to their home in Bel-Air, Los Angeles, had its address changed from 666 St. Cloud Road to 668 St. Cloud Road. Another well-known example was the U.S. Route 666, where accidents and incidents were common. It is known as "Devil's Highway" and renamed to U.S. Route 491.