113 (number)

Mathematics

• 113 is the natural number following 112 and preceding 114.
• It is the 30th prime number, so it can only be divided by one and itself. 113 is a Sophie Germain prime, a Chen prime and a Proth prime as it is a prime number of the form 7 × 2⁴ + 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, and a permutable prime with 131 and 311.
• 113 is a highly cototient number and a centered square number.
• 355/113 approximates pi to six decimal places, with an error of less than 1/113³. 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.

  Religion

• 113, the number of surah 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

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

  Telephony

• 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

  Other uses

• 113, 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"