75 (number)

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

← 74 76 → 75
← 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)
Numeral system	75
Factorization	$3 \cdot 5^2$
Divisors	1, 3, 5, 15, 25, 75
Roman numeral	LXXV
Binary	10010112
Octal	1138
Duodecimal	6312
Hexadecimal	4B16

In mathematics

As the sum of the first five pentagonal numbers, seventy-five 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:

• Diamond anniversary^{[citation needed]}
• The atomic number of rhenium
• The age limit for Canadian senators^{[citation needed]}
• Municipal Okrug 75, a municipal okrug of Frunzensky District of Saint Petersburg, Russia
• A common name for the Canon de 75 modèle 1897, a French World War 1 gun
• The departement number of the city of Paris