9 (nine) is a positive integer following 8 and preceding 10. Its ordinal form is written "9th" or "ninth".
9 is the smallest number that is both odd and composite. It is the 3rd square number.
- 9 is also equal to !4 using subfactorial.
- Its prime factorization is 9 = 3².
- 9 is one of two known odd unitary superperfect numbers. The other one is 165.
- A 9 sided polygon is called an enneagon or a nonagon.
- Some googologisms based on 9 are googolnoniplex and superenn.
- 9 can be named "garthree" with the gar- prefix.
- In Greek-based number naming systems, 9 is associated with prefix ennea-, and with prefix nona- or novem- in Latin systems
- Username5243 coined the name Ternary-Goodol for this number, and it's equal to 32 in Username5243's Array Notation.
- Binary198 calls this number hyper, and it's equal to \([2,\omega^2]\) using Ordinal Array Notation.
Googological functions returning 9