121 (one hundred [and] twenty-one) is the natural number following 120 and preceding 122.
| ||||
---|---|---|---|---|
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 | |||
Senary | 3216 | |||
Octal | 1718 | |||
Duodecimal | A112 | |||
Hexadecimal | 7916 |
In mathematics
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 ternary. Furthermore, 121 is the only square of the form
, where p is prime (3, in this case).[1]
- the sum of three consecutive prime numbers (37 + 41 + 43).
- As
, it provides a solution to Brocard's problem. There are only two other squares known to be of the form
. 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
(with x being 2 and 5, respectively).[2]
- It is also a star number, a centered tetrahedral number, and a centered octagonal number.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Chinese_checkers_start_positions.svg/220px-Chinese_checkers_start_positions.svg.png)
- In decimal, 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 (
). But it cannot 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[3]
- The undiscovered chemical element unbiunium has the atomic number 121
- The official end score for cribbage[4]
- The pennant number of RTS Moskva, the Russian Navy’s Black Sea flagship, which was damaged beyond repair on April 13, 2022.
See also
References
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