121 (number)
121 is the natural number following 120 and preceding 122.
| ||||
---|---|---|---|---|
Cardinal | one hundred [and] twenty-one | |||
Ordinal | st | |||
Numeral system | 121 | |||
Factorization | ||||
Divisors | 1, 11, 121 | |||
Greek numeral | ΡΚΑ´ | |||
Roman numeral | CXXI | |||
Binary | 11110012 | |||
Ternary | 111113 | |||
Senary | 3216 | |||
Octal | 1718 | |||
Duodecimal | A112 | |||
Hexadecimal | 7916 |
In mathematics
One hundred [and] 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 , 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 Brocard's 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 x3 - 4 (with x being 2 and 5, respectively).[1]
It is also a star number and a centered octagonal number.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/0/08/Chinese_checkers_start.svg/220px-Chinese_checkers_start.svg.png)
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
121 is also:
- The electricity emergency telephone number in Egypt
- The number for voicemail for mobile phones on the Vodafone network[citation needed]
- The number of points required to win a standard game of Cribbage[citation needed]
- The undiscovered chemical element Unbiunium has the atomic number 121
See also
- List of highways numbered 121
- United States House of Representatives House Resolution 121
- United Nations Security Council Resolution 121
References
- ^ Wells, D. The Penguin Dictionary of Curious and Interesting Numbers London: Penguin Group. (1987): 136