31 (number)
| ||||
|---|---|---|---|---|
| Cardinal | thirty-one | |||
| Ordinal | 31st (thirty-first) | |||
| Factorization | prime | |||
| Prime | 11th | |||
| Divisors | 1, 31 | |||
| Greek numeral | ΛΑ´ | |||
| Roman numeral | XXXI, xxxi | |||
| Binary | 111112 | |||
| Ternary | 10113 | |||
| Senary | 516 | |||
| Octal | 378 | |||
| Duodecimal | 2712 | |||
| Hexadecimal | 1F16 | |||
31 (thirty-one) is the natural number following 30 and preceding 32.
Mathematics
[edit]31 is a prime number, a twin prime[1][2] (with 29), a super-prime, a member of an emirp prime pair,[3] a sexy prime, and a Mersenne prime.[4] Since it is a Mersenne prime, it can be expressed as 25 - 1.[2]
31 is a centered triangular number, a centered pentagonal number, and a centered decagonal number.[2]
(bottom left)
31 shown as a centered pentagonal, triangular, and decagonal number.
In other fields
[edit]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
[edit]- ↑ 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.
- 1 2 3 Vanovschi, Vitalii. "Properties of the number 31". www.numberempire.com. Retrieved 2026-08-23.
- ↑ Weisstein, Eric W. "Emirp". mathworld.wolfram.com. Wolfram Research, Inc. Retrieved 2026-09-01.
- ↑ 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.
External links
[edit]
Look up thirty-one in Wiktionary, the free dictionary.
Wikimedia Commons has media related to 31 (number).
- Prime Curios! 31 from the Prime Pages
| |||||||||
| |||||||||
| |||||||||
| |||||||||
