666

666 (six hundred sixty-six) is a natural number that follows 665 and precedes 667. It is a composite number with prime factorization 2 × 3^2 × 37. It is the 36th triangular number, since 36 × 37 / 2 = 666. In Roman numerals it is written as DCLXVI, a descending sequence using each of the standard symbols exactly once. In base-10, the sum of its digits is 18, making 666 a Harshad (Niven) number, as it is divisible by 18. It is also an abundant number, since the sum of its proper divisors (816) exceeds 666.

In religious contexts, 666 is described in the Book of Revelation as the number of the beast. The text notes that the number represents a man’s number and has led to centuries of interpretation and debate. Some manuscripts state 616 as an alternate value. In scholarship, the figure is commonly treated as symbolic rather than a precise prediction, often associated with imperfection or malevolent power.

Beyond scripture, 666 has a prominent place in popular culture as a symbol linked to the devil and ominous themes in films, music, and literature. In contemporary online culture, 666 appears in various memes and if interpreted in East Asian contexts, the digit 6 is sometimes considered lucky or auspicious; repetition like “666” can be used to express praise or admiration, akin to “cool” or “awesome.” In the United States, U.S. Route 666—a highway running through several states—was renumbered to U.S. Route 491 in 2003 due to the number’s negative associations.