31 (number)

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← 30 31 32 →
Cardinalthirty-one
Ordinal31st
(thirty-first)
Factorizationprime
Prime11th
Divisors1, 31
Greek numeralΛΑ´
Roman numeralXXXI, xxxi
Binary111112
Ternary10113
Senary516
Octal378
Duodecimal2712
Hexadecimal1F16

31 (thirty-one) is the natural number following 30 and preceding 32. It is a prime number.

Mathematics

31 is a prime number, a twin prime[1] (with 29), a super-prime, a member of an emirp prime pair, a sexy prime, and a Mersenne prime.[2]

31 is a centered pentagonal number.

In other fields

31 equal temperament is a popular microtonal tuning for musical instruments because it provides a good approximation of harmonic intervals.

January, March, May, July, August, October and December have 31 days.

31 is the international calling code for the Netherlands.

Notes

References