What is the 20th prime number?
The 20th prime number is 71. The next prime is 73 (a gap of 2) and the one before is 67.
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 20th one is 71.
- 2
71 is prime because no prime up to ā71 ā 8.43 divides it.
- 3
The primes are spread thinner as numbers grow: by the prime number theorem the 20th prime is close to 20 Ć ln(20) ā 60, and here it is 71.
- 4
71 is a twin prime: 71 and 73 are both prime.
Primes around the 20th
| Position | Prime | Gap from the previous |
|---|---|---|
| 17 | 59 | 6 |
| 18 | 61 | 2 |
| 19 | 67 | 6 |
| 20 | 71 | 4 |
| 21 | 73 | 2 |
| 22 | 79 | 6 |
| 23 | 83 | 4 |
Questions
What is the 20th prime number?
71.
Which prime number is 71?
71 is the 20th prime number.
What is the sum of the first 20 primes?
639.