|Cardinal||One hundred [and]|
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 , where p is prime (3, in this case). There are only two other squares known to be of the form n! + 1.
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. But it can not be expressed as the sum of any other number plus that number's digits, making 121 a self number.
One hundred twenty-one is also:
- The number for voicemail for mobile phones on the Vodafone network
- The model number of the Lockheed EC-121, now on display at the Air Force Museum.
- The year AD 121 or 121 BC.