Thirty-one
| Thirty-one | |
|---|---|
| 31 | |
| presentation | |
| Roman | XXXI |
| dual | 1 1111 |
| Octal | 37 |
| Duodecimal | 27 |
| Hexadecimal | 1F |
| Morse code | · · · - - · - - - - |
| Chinese | 三十 一, 參 拾 壹 |
| Mathematical properties | |
| sign | positive |
| parity | odd |
| Factorization | Prime number |
The thirty-one (31) is the natural number between thirty and thirty-two . It is odd and a prime number .
mathematics
Thirty-one is the third Mersenne prime .
Thirty-one is a centered triangular number , a centered pentagonal number, and a centered decagonal number.
For the Steiner tree problem , thirty-one is the number of possible Steiner topologies for Steiner trees with 4 endpoints.
Thirty-one is also a happy number and a happy number .
In addition, 31 10 is a Devlali number, which means it cannot be generated from the sum of any other whole number and its digits.
31, 331, 3331, 33331, 333331, 3333331, and 33333331 are all prime numbers. It was therefore assumed that any number of the form 3 w 1 represents a prime number. This assumption has been refuted today as the next nine examples in this series are not prime numbers:
- 333333331 = 17 × 19607843
- 3333333331 = 673 × 4952947
- 33333333331 = 307 × 108577633
- 333333333331 = 19 × 83 × 211371803
- 3333333333331 = 523 × 3049 × 2090353
- 33333333333331 = 607 × 1511 × 1997 × 18199
- 333333333333331 = 181 × 1841620626151
- 3333333333333331 = 199 × 16750418760469 and
- 33333333333333331 = 31 × 1499 × 717324094199.
science
chemistry
31 is the atomic number of gallium .
astronomy
- the Andromeda Galaxy is listed in the Messier catalog as M31
- NGC 31 denotes a spiral galaxy in the constellation Phoenix
Culture and language
Thirty-one is the name of two games of chance with playing cards , namely for:
- the old French game Trente-et-un , which later resulted in Seventeen and Four and Black Jack and
- the card game swimming .
In the youth language, a 31er is a traitor or nest-defiler. The term originally refers to Section 31 of the Narcotics Act .
Trivia
- The number of triads in music (12 large, 12 small, 4 diminished and 3 excessive).
- The number of days in January , March , May , July , August , October, and December .
- The international phone code for the Netherlands .
- ISO 31 is an international standard for sizes and units.
- The title of a book by Gerald Ganglbauer : "Thirty-one" (2015).
- The title of a book by Nick Hornby : "31 Songs" (2003).
- The Haute-Garonne department is the 31st French department .
- Villa 31 , slum in Buenos Aires