25 (number)


25 is the natural number following 24 and preceding 26.

In mathematics

It is a square number, being 52 = 5 × 5. It is one of two two-digit numbers whose square and higher powers of the number also ends in the same last two digits, e.g. 252 = 625, the other is 76. It is the smallest square that is also a sum of two squares: 25 = 32 + 42. Hence it often appears in illustrations of the Pythagorean theorem.
25 is the sum of the single-digit odd natural numbers 1, 3, 5, 7 and 9, the first five odd natural numbers.
25 is a centered octagonal number, a centered square number, and an automorphic number.
25 percent is equal to.
It is the smallest base 10 Friedman number as it can be expressed by its own digits: 52.
It is also a Cullen number. 25 is the smallest pseudoprime satisfying the congruence 7n = 7 mod n.
25 is the smallest aspiring number — a composite non-sociable number whose aliquot sequence does not terminate.
According to the Shapiro inequality, 25 is the least odd integer n such that there exist x, x,..., x such that
where x = x, x = x.
Within base 10 one can readily test for divisibility by 25 by seeing if the last two digits of the number match 00, 25, 50 or 75.

In science

Twenty five is: