Prime numbers between 1 and 100
There are 25 prime numbers between 1 and 100: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97.
How to work it out
- 1
A prime has exactly two factors, 1 and itself. To list them, cross out multiples of 2, then 3, then 5, and so on up to ā100 ā 10.0 (the sieve of Eratosthenes). What is left are the primes.
- 2
That leaves 25 primes between 1 and 100, with a total of 1,060.
- 3
The biggest gap between neighbouring primes in this range is 8, after 89 (the next prime is 97). There are 8 twin prime pairs (primes 2 apart): (3, 5), (5, 7), (11, 13), (17, 19), (29, 31), (41, 43), (59, 61), (71, 73).
How many primes in each part
| Range | Primes | Share of the numbers |
|---|---|---|
| 1 to 10 | 4 | 40% |
| 11 to 20 | 4 | 40% |
| 21 to 30 | 2 | 20% |
| 31 to 40 | 2 | 20% |
| 41 to 50 | 3 | 30% |
| 51 to 60 | 2 | 20% |
| 61 to 70 | 2 | 20% |
| 71 to 80 | 3 | 30% |
| 81 to 90 | 2 | 20% |
| 91 to 100 | 1 | 10% |
Questions
How many prime numbers are there between 1 and 100?
25.
What is the biggest prime number below 100?
97.
What is the first prime number after 0?
2.