even, composite, triangular, palindrome · 666th positive integer
The number 666
666 is an even composite number. It's known as the "number of the beast" in the Book of Revelation. It is the 666th positive integer.
Quick reference
| Prime factorization | 2 × 3 × 3 × 37 |
| Divisors | 1, 2, 3, 6, 9, 18, 37, 74, 111, 222, 333, 666 |
| Binary | 1010011010 |
| Hexadecimal | 0x29A |
| Roman numeral | DCLXVI |
| Digit sum | 18 |
| Properties | even, composite, triangular, palindrome |
Why 666 is notable
The "number of the beast" in the Book of Revelation.
Reading 666 in NumGrid context
666 is one of the data points covered by this site’s integer properties and number-guessing puzzles dataset. The detail above comes directly from classical number theory plus NumGrid solver-derived puzzle statistics; the context that follows situates the headline numbers against the broader distribution across positive integers within the NumGrid target pool.
Every number on this page links back to classical number theory plus NumGrid solver-derived puzzle statistics; the methodology page describes the inputs, refresh cadence, and known limitations of the underlying data product.
For readers using this page as a decision input, the related-entity pages elsewhere on the site provide the comparison set. The most useful comparison for 666 is typically a peer within positive integers within the NumGrid target pool with similar size, similar exposure, or similar geography — not the national-level summary alone.
Frequently asked
Is 666 a prime number?
No. 666 is composite. Its prime factorization is 2 × 3 × 3 × 37.
What are the factors of 666?
The factors (divisors) of 666 are 1, 2, 3, 6, 9, 18, 37, 74, 111, 222, 333, 666.
What is 666 in binary?
666 in binary is 1010011010. In hexadecimal it's 29A.
What is 666 as a Roman numeral?
666 in Roman numerals is DCLXVI.
What's the digit sum of 666?
Adding the digits of 666: 6 + 6 + 6 = 18.