666 is the natural number following 665 and preceding 667. It is a composite number.
666 is often associated with Satan, who is illustrated here in an engraved interpretation by Gustave Doré.
A 666 float in a Paris street parade
Satan, also known as the Devil, is an entity in Abrahamic religions who entices humans into sin or falsehood. In Judaism, Satan is seen as an agent subservient to God, typically regarded as a metaphor
666 (number)
…sum of the first thirty-six natural numbers, which makes it a triangular number: In Christian religion Number of the beast 666 is often associated with Satan, who is illustrated here in an engraved interpretation by Gustave Doré. In the Textus Receptus manuscripts of the New Testament, the Book of Revelation…
Illustration of the Devil on Codex Gigas, early thirteenth century
Balaam and the Angel (1836) by Gustav Jäger. The angel in this incident is referred to as a "satan".
The Examination of Job (c. 1821) by William Blake
The sound of a shofar (pictured) is believed to symbolically confuse Satan.