What is the 121st prime number?
The 121st prime number is 661. The next prime is 673 (a gap of 12) and the one before is 659.
Position
Pick any whole number from 1 to 10,000.
How to work it out
- 1
List the primes in order: 2, 3, 5, 7, 11, 13, ā¦ The 121st one is 661.
- 2
661 is prime because no prime up to ā661 ā 25.71 divides it.
- 3
The primes are spread thinner as numbers grow: by the prime number theorem the 121st prime is close to 121 Ć ln(121) ā 580, and here it is 661.
- 4
661 is a twin prime: 659 and 661 are both prime.
Primes around the 121st
| Position | Prime | Gap from the previous |
|---|---|---|
| 118 | 647 | 4 |
| 119 | 653 | 6 |
| 120 | 659 | 6 |
| 121 | 661 | 2 |
| 122 | 673 | 12 |
| 123 | 677 | 4 |
| 124 | 683 | 6 |
Questions
What is the 121st prime number?
661.
Which prime number is 661?
661 is the 121st prime number.
What is the sum of the first 121 primes?
36,888.