- 25 is an odd number.
- 25 is the 5th square number.
- 25 is the result of the Pythagorean triple 32+42 or 9+16=25.
- Its prime factorization is 25 = 5².
- 25 is the first Friedman number.
Counting to 25 using fingers
It is possible to extend standard counting system so that it can count up to 25. The matter is that when we bend the first five fingers on one hand, we bend one on another hand and unbend all on the first. Extension of this method can be used to count all the way to 1,023, using powers of 2.
- In Greek-based number-naming systems, 25 is associated with the prefix "pentaicosa-", and with the prefix "quinviginti-" in Latin systems.
- It can be named garfive with the gar- prefix.
As a cash denomination
- OEIS, Sequence A000290