odd, prime, Fibonacci · 13th positive integer
The number 13
13 is an odd prime number. It's known as famously considered unlucky in Western culture; a Fibonacci number. It is the 13th positive integer.
Quick reference
| Prime factorization | 13 (prime) |
| Divisors | 1, 13 |
| Binary | 1101 |
| Hexadecimal | 0xD |
| Roman numeral | XIII |
| Digit sum | 4 |
| Properties | odd, prime, Fibonacci |
Why 13 is notable
Famously considered unlucky in Western culture; a Fibonacci number.
Reading 13 in NumGrid context
13 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.
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.
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 13 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 13 a prime number?
Yes. 13 is prime — its only divisors are 1 and itself.
What are the factors of 13?
The factors (divisors) of 13 are 1, 13.
What is 13 in binary?
13 in binary is 1101. In hexadecimal it's D.
What is 13 as a Roman numeral?
13 in Roman numerals is XIII.
What's the digit sum of 13?
Adding the digits of 13: 1 + 3 = 4.