75 (number)

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

← 74 75 76 →
← 70 71 72 73 74 75 76 77 78 79 → List of numbers Integers ← 0 10 20 30 40 50 60 70 80 90 →
Cardinal	seventy-five
Ordinal	75th (seventy-fifth)
Factorization	3 × 52
Divisors	1, 3, 5, 15, 25, 75
Greek numeral	ΟΕ´
Roman numeral	LXXV, lxxv
Binary	10010112
Ternary	22103
Senary	2036
Octal	1138
Duodecimal	6312
Hexadecimal	4B16

In mathematics

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.