Concept
25 (twenty-five) is the natural number following 24 and preceding 26. It is a square number, being 52 = 5 × 5, and hence the third non-unitary square prime of the form p2. 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. Twenty five has an even aliquot sum of 6, which is itself the first even and perfect number root of an aliquot sequence; not ending in (1 and 0). It is the smallest square that is also a sum of two (non-zero) squares: 25 = 32 + 42. Hence, it often appears in illustrations of the Pythagorean theorem. 25 is the sum of the five consecutive single-digit odd natural numbers 1, 3, 5, 7, and 9. 25 is a centered octagonal number, a centered square number, a centered octahedral number, and an automorphic number. 25 percent (%) is equal to 1/4. It is the smallest decimal Friedman number as it can be expressed by its own digits: 52. It is also a Cullen number and a vertically symmetrical 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 smallest odd integer n such that there exist x_1, x_2, ..., x_n such that where x_n + 1 = x_1, x_n + 2 = x_2. Within decimal, one can readily test for divisibility by 25 by seeing if the last two digits of the number match 00, 25, 50, or 75. There are 25 primes under 100. The Standard Model of physics features a total of 25 elementary particles: 12 fermions (made of 6 quarks and 6 leptons) and 13 bosons (made of 12 gauge bosons and 1 scalar boson). The atomic number of manganese. The average percentage DNA overlap of an individual with their half-sibling, grandparent, grandchild, aunt, uncle, niece, nephew, identical twin cousin (offspring of identical twins), or double cousin. In Ezekiel's vision of a new temple: The number twenty-five is of cardinal importance in Ezekiel's Temple Vision (in the Bible, Ezekiel chapters 40–48).