666
666 is a repdigit best known as the 'Number of the Beast' referenced in the Book of Revelation.
- Even
- Composite
Where 666 fits
Why 666 is special
666's religious and popular-culture notoriety is far larger than its mathematical profile as an ordinary composite, triangular repdigit.
666 is part of
Factors & digit properties
- Divisors (12)
- 1, 2, 3, 6, 9, 18, 37, 74, 111, 222, 333, 666
- Prime factorisation
- 2 × 3^2 × 37
- Digit sum
- 18
- Digital root
- 9
Representations
- Decimal
- 666
- Binary
- 1010011010
- Octal
- 1232
- Hexadecimal
- 29a
- Roman numeral
- DCLXVI
- Scientific notation
- 6.660 × 10^2
Other mathematical patterns
- Triangular number
- Palindromic number
- Abundant number
- Repdigit
- Harshad (Niven) number
Related numbers & connections
666 is referred to as the 'number of the beast' in the Book of Revelation.
Other connections
- is associated with"Number of the Beast" (Book of Revelation)
why?
Strength 0.50, confidence "high".
Religion & belief
666 is referred to as the 'number of the beast' in the Book of Revelation (13:18) of the Christian New Testament; some early manuscripts instead give 616. Its later association with the occult and popular superstition is a separate, later cultural development distinct from the original text.
DocumentedReligion & belief
Common questions
Is 666 a prime number?
No, 666 is not prime.
What are the factors of 666?
The factors of 666 are 1, 2, 3, 6, 9, 18, 37, 74, 111, 222, 333, 666.
What is 666 in Roman numerals?
666 in Roman numerals is DCLXVI.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 1 reviewer-confirmed record, sourced and reviewed before publication.
Last reviewed: 15 July 2026