75 (seventy-five) is the natural number following 74 and preceding 76.

75 is a self number because there is no integer that added up to its own digits adds up to 75.^[1] It is the sum of the first five pentagonal numbers, and therefore a pentagonal pyramidal number, as well as a nonagonal number.^[2][3]

It is also the fourth ordered Bell number, and a Keith number, because it recurs in a Fibonacci-like sequence started from its base 10 digits: 7, 5, 12, 17, 29, 46, 75...^[4]

75 is the count of the number of weak orderings on a set of four items.^[5]

Excluding the infinite sets, there are 75 uniform polyhedra in the third dimension, which incorporate star polyhedra as well. Inclusive of 7 families of prisms and antiprisms, there are also 75 uniform compound polyhedra.