odd, prime · 31st positive integer
The number 31
31 is an odd prime number. It is the 31st positive integer.
Quick reference
| Prime factorization | 31 (prime) |
| Divisors | 1, 31 |
| Binary | 11111 |
| Hexadecimal | 0x1F |
| Roman numeral | XXXI |
| Digit sum | 4 |
| Properties | odd, prime |
Reading 31 in NumGrid context
For 31, the underlying data on this page comes from classical number theory plus NumGrid solver-derived puzzle statistics. The breakdown above is the federal record; the paragraphs below add the per-entity context that makes the headline numbers usable for a real decision rather than just a data lookup.
The methodology behind every numeric value on this page is publicly documented on the classical number theory plus NumGrid solver-derived puzzle statistics portal and described in detail on this site’s methodology page. Refresh cadence varies by underlying series; the page surfaces the as-of date for each number so readers can trace any figure back to the source release.
Practical use of this page is in combination with the comparison and ranking pages elsewhere on the site, which surface the same data for 31’s peers within positive integers within the NumGrid target pool. A single-entity reading without peer context can be misleading when an entity is an outlier on one axis but typical on another.
Frequently asked
Is 31 a prime number?
Yes. 31 is prime — its only divisors are 1 and itself.
What are the factors of 31?
The factors (divisors) of 31 are 1, 31.
What is 31 in binary?
31 in binary is 11111. In hexadecimal it's 1F.
What is 31 as a Roman numeral?
31 in Roman numerals is XXXI.
What's the digit sum of 31?
Adding the digits of 31: 3 + 1 = 4.