Is 721 a prime number?
No, 721 is not a prime number. It is divisible by 7: 721 = 7 × 103.
Is 721 prime?
Pick any whole number from 1 to 10,000.
How to work it out
- 1
A prime number has exactly two factors: 1 and itself.
- 2
It is enough to test the primes up to √721 ≈ 26.85. If none of them divides 721, it is prime.
- 3
7 divides 721 exactly, so it is not prime. Its prime factorisation is
LaTeX source of the formulas on this page
\[ 721 = 7 \times 103 \]
Testing 721 by the primes up to its square root
| Prime | Division | Result |
|---|---|---|
| 2 | 721 ÷ 2 | leaves 1 |
| 3 | 721 ÷ 3 | leaves 1 |
| 5 | 721 ÷ 5 | leaves 1 |
| 7 | 721 ÷ 7 | divides exactly (103) |
| 11 | 721 ÷ 11 | leaves 6 |
| 13 | 721 ÷ 13 | leaves 6 |
| 17 | 721 ÷ 17 | leaves 7 |
| 19 | 721 ÷ 19 | leaves 18 |
| 23 | 721 ÷ 23 | leaves 8 |
Questions
Is 721 a prime number?
No, 721 is not a prime number. It is divisible by 7: 721 = 7 × 103.
What is the next prime after 721?
727.
What is the prime number before 721?
719.
What are the factors of 721?
1, 7, 103, 721.