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31 (number)

From Wikipedia, the free encyclopedia
(Redirected from Number 31)
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.

Mathematics

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31 is a centered pentagonal number.

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]


In other fields

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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.

References

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  1. Sloane, N. J. A. (ed.). "Sequence A077800 (List of twin primes {p, p+2}.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2023-06-07.
  2. Sloane, N. J. A. (ed.). "Sequence A000668 (Mersenne primes (primes of the form 2^n - 1).)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2023-06-07.
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