# 75 (number)

 ← 74 75 76 →
Cardinal seventy-five
Ordinal 75th
(seventy-fifth)
Factorization 3 × 52
Divisors 1, 3, 5, 15, 25, 75
Roman numeral LXXV
Binary 10010112
Ternary 22103
Quaternary 10234
Quinary 3005
Senary 2036
Octal 1138
Duodecimal 6312
Vigesimal 3F20
Base 36 2336

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

## In mathematics

75 is the fourth ordered Bell number, and counts the number of weak orderings on a set of four items.

As the sum of the first five pentagonal numbers, 75 is a pentagonal pyramidal number. It is also an enneagonal number.

It is also a Keith number, because it recurs in a Fibonacci-like sequence started from its base 10 digits: 7, 5, 12, 17, 29, 46, 75... But there is no integer that added up to its own digits adds up to 75, hence 75 is a self number.

Excluding the infinite sets, there are 75 uniform polyhedra (or 76 if edges are allowed to coincide).

## In other fields

Seventy-five is also:

## References

1. ^ “Who are our senators and what do they do?”, Parliament of Canada, retrieved 2014-02-02.