odd, composite, perfect square, palindrome · 9th positive integer
The number 9
9 is an odd composite number. It's known as the largest single digit. It is the 9th positive integer.
Quick reference
| Prime factorization | 3 × 3 |
| Divisors | 1, 3, 9 |
| Binary | 1001 |
| Hexadecimal | 0x9 |
| Roman numeral | IX |
| Digit sum | 9 |
| Properties | odd, composite, perfect square, palindrome |
Why 9 is notable
The largest single digit.
Reading 9 in NumGrid context
For 9, 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 9’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 9 a prime number?
No. 9 is composite. Its prime factorization is 3 × 3.
What are the factors of 9?
The factors (divisors) of 9 are 1, 3, 9.
What is 9 in binary?
9 in binary is 1001. In hexadecimal it's 9.
What is 9 as a Roman numeral?
9 in Roman numerals is IX.
What's the digit sum of 9?
Adding the digits of 9: 9 = 9.