# ⓘ 121 (number)

## ⓘ 121 (number)

One hundred twenty-one is a square and is the sum of three consecutive primes 37 + 41 + 43. There are no squares besides 121 known to be of the form 1 + p + p 2 + p 3 + p 4 {\displaystyle 1+p+p^{2}+p^{3}+p^{4}}, where p is prime 3, in this case. Other such squares must have at least 35 digits.

There are only two other squares known to be of the form n! + 1, supporting Brocards conjecture. Another example of 121 being of the few examples supporting a conjecture is that Fermat conjectured that 4 and 121 are the only perfect squares of the form x 3 - 4 with x being 2 and 5, respectively.

It is also a star number and a centered octagonal number.

In base 10, it is a Smith number since its digits add up to the same value as its factorization which uses the same digits and as a consequence of that it is a Friedman number 11^2. But it can not be expressed as the sum of any other number plus that numbers digits, making 121 a self number.

## 1. In other fields

121 is also:

• The undiscovered chemical element Unbiunium has the atomic number 121
• The number for voicemail for mobile phones on the Vodafone network
• The electricity emergency telephone number in Egypt
• The official end score for Cribbage

• The 121 series 121 系 is an electric multiple unit EMU train type introduced in March 1987 by Japanese National Railways JNR and currently operated
• Coordinates: 39 20 04 N 121 39 44 W 39.33444 N 121 66222 W 39.33444 - 121 66222 Gridley Colony Number One is a former settlement in Butte County
• Coordinates: 39 21 03 N 121 39 44 W 39.35083 N 121 66222 W 39.35083 - 121 66222 Gridley Colony Number Two is a former settlement in Butte County
• The Morane - Saulnier MoS - 121 also known as the Morane - Saulnier MS. 121 was a French fighter prototype of the 1920s. It was Morane - Saulnier s first fighter
• TS - 121 is an orally active, selective vasopressin V1B receptor antagonist which is under development by Taisho Pharmaceutical for the adjunctive treatment
• palindromic perfect powers nk, where n is a natural number and k is 2, 3 or 4. Palindromic squares: 0, 1, 4, 9, 121 484, 676, 10201, 12321, 14641, 40804, 44944
• The Boeing CQM - 121 Pave Tiger was an unmanned aerial vehicle developed by Boeing for use by the United States Air Force. Intended for the Suppression
• renumbering, SR 121 was known as Secondary State Highway 1M, linking Rochester to Maytown. Between the renumbering and 1967, the highway was numbered Sign Route
• M 121 or M - 121 may refer to: M 121 A1 155mm Cartridge, a U.S. Army chemical artillery shell M - 121 bomb a World War II bomb M 121 mortar carrier, the United
• The I - 121 - class submarine 伊百二十一型潜水艦, I - hyaku - ni - jū - ichi - gata sensuikan was a class of submarine in the Imperial Japanese Navy IJN serving from the

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