121 (number)
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Cardinal | one hundred twenty-one | |||
Ordinal | 121st (one hundred twenty-first) | |||
Factorization | 112 | |||
Divisors | 1, 11, 121 | |||
Greek numeral | ΡΚΑ´ | |||
Roman numeral | CXXI | |||
Binary | 11110012 | |||
Ternary | 111113 | |||
Octal | 1718 | |||
Duodecimal | A112 | |||
Hexadecimal | 7916 |
121 (one hundred [and] twenty-one) is the natural number following 120 and preceding 122.
In mathematics[edit]
One hundred [and] twenty-one is
- a square (11 times 11)
- the sum of the powers of 3 from 0 to 4, so a repunit in base 3. Furthermore 121 is the only square of the form , where p is prime (3, in this case).[citation needed]
- the sum of three consecutive primes (37 + 41 + 43).
- As 5! + 1 = 121 it provides a solution to Brocard's problem. There are only two other squares known to be of the form n! + 1, . Another example of 121 being one of the few numbers supporting a conjecture is that Fermat conjectured that 4 and 121 are the only perfect squares of the form x3 - 4 (with x being 2 and 5, respectively).[1]
- It is also a star number and a centered octagonal number.
![](http://webcf.waybackmachine.org/web/20220421193753im_/https://upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Chinese_checkers_start_positions.svg/220px-Chinese_checkers_start_positions.svg.png)
A Chinese checkers board has 121 holes
- 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 number's digits, making 121 a self number.
In other fields[edit]
121 is also:
- The electricity emergency telephone number in Egypt
- The number for voicemail for mobile phones on the Vodafone network[2]
- The undiscovered chemical element unbiunium has the atomic number 121
- The official end score for cribbage[3]
See also[edit]
- List of highways numbered 121
- United States House of Representatives House Resolution 121
- United Nations Security Council Resolution 121
References[edit]
- ^ Wells, D., The Penguin Dictionary of Curious and Interesting Numbers, London: Penguin Group. (1987): 136
- ^ Vodafone, Calling and messaging
- ^ Rule 1.1 Archived 2015-01-18 at the Wayback Machine, American Cribbage Congress, retrieved 6 September 2011