odd, composite · 391st positive integer
The number 391
391 is an odd composite number. It is the 391st positive integer.
Quick reference
| Prime factorization | 17 × 23 |
| Divisors | 1, 17, 23, 391 |
| Binary | 110000111 |
| Hexadecimal | 0x187 |
| Roman numeral | CCCXCI |
| Digit sum | 13 |
| Properties | odd, composite |
Reading 391 in NumGrid context
391 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 391 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 391 a prime number?
No. 391 is composite. Its prime factorization is 17 × 23.
What are the factors of 391?
The factors (divisors) of 391 are 1, 17, 23, 391.
What is 391 in binary?
391 in binary is 110000111. In hexadecimal it's 187.
What is 391 as a Roman numeral?
391 in Roman numerals is CCCXCI.
What's the digit sum of 391?
Adding the digits of 391: 3 + 9 + 1 = 13.