# 113 (number)

| ||||
---|---|---|---|---|

Cardinal | one hundred thirteen | |||

Ordinal |
113th (one hundred thirteenth) | |||

Factorization | prime | |||

Prime | 30th | |||

Divisors | 1, 113 | |||

Greek numeral | ΡΙΓ´ | |||

Roman numeral | CXIII | |||

Binary |
1110001_{2} | |||

Ternary |
11012_{3} | |||

Quaternary |
1301_{4} | |||

Quinary |
423_{5} | |||

Senary |
305_{6} | |||

Octal |
161_{8} | |||

Duodecimal |
95_{12} | |||

Hexadecimal |
71_{16} | |||

Vigesimal |
5D_{20} | |||

Base 36 |
35_{36} |

The number **113** (**one hundred [and] thirteen**) is used in many contexts.

## Mathematics[edit]

- 113 is the natural number following 112 and preceding 114.
- It is the 30th prime number (following 109 and preceding 127), so it can only be divided by one and itself. 113 is a Sophie Germain prime,
^{[1]}a Chen prime^{[2]}and a Proth prime as it is a prime number of the form 7 × 2^{4}+ 1. 113 is also an Eisenstein prime with no imaginary part and real part of the form . In base 10, this prime is a primeval number,^{[3]}and a permutable prime with 131 and 311. - 113 is a highly cototient number
^{[4]}and a centered square number.^{[5]} - 355/113 approximates pi to six decimal places, with an error of less than 1/113
^{3}. This means that 113/355 approximates the reciprocal of pi. - 113 is the smallest positive integer that cannot be represented in the Four fours problem using standard rules.
^{[clarification needed]}^{[dubious – discuss]}

## Religion[edit]

- 113, the number of surat al-Falaq in the Qur'an
- Psalms 113–118 constitute the Hallel, which is recited on the three great feasts: Passover, Weeks, and Tabernacles

## Science[edit]

- 113, the atomic number of the element Nihonium
- Cadmium-113m, a radioisotope and nuclear isomer with a halflife of 14.1 years

## Telephony[edit]

113 is:

- The fire emergency telephone number in Indonesia
- The intelligence agency telephone number in Iran
- The medical emergency telephone number in Latvia and Norway
- The police emergency telephone number in Italy, Luxembourg, Slovenia, and Vietnam
- The time telephone number in Argentina
- The mental health crisis hotline telephone number in the Netherlands

## Other uses[edit]

- 113 (band), a French hip hop group
- 113, the port number of the IDENT Internet protocol that helps identify the user of a particular TCP connection
- 113, in enduro, is regarded as an unlucky number to be given to a race entrant and is colloquially known as a "blind pew"

## See also[edit]

## References[edit]

**^**"Sloane's A005384 : Sophie Germain primes".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-26.**^**"Sloane's A109611 : Chen primes".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-26.**^**"Sloane's A072857 : Primeval numbers".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-26.**^**"Sloane's A100827 : Highly cototient numbers".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-26.**^**"Sloane's A001844 : Centered square numbers".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-26.

- Wells, D.
*The Penguin Dictionary of Curious and Interesting Numbers*London: Penguin Group. (1987): 134