Is 821 a prime number?
Yes, 821 is a prime number. Its only factors are 1 and 821.
Is 821 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 √821 ≈ 28.65. If none of them divides 821, it is prime.
- 3
None of them divides 821, so it is prime.
Testing 821 by the primes up to its square root
| Prime | Division | Result |
|---|---|---|
| 2 | 821 ÷ 2 | leaves 1 |
| 3 | 821 ÷ 3 | leaves 2 |
| 5 | 821 ÷ 5 | leaves 1 |
| 7 | 821 ÷ 7 | leaves 2 |
| 11 | 821 ÷ 11 | leaves 7 |
| 13 | 821 ÷ 13 | leaves 2 |
| 17 | 821 ÷ 17 | leaves 5 |
| 19 | 821 ÷ 19 | leaves 4 |
| 23 | 821 ÷ 23 | leaves 16 |
Questions
Is 821 a prime number?
Yes, 821 is a prime number. Its only factors are 1 and 821.
What is the next prime after 821?
823.
What is the prime number before 821?
811.
What are the factors of 821?
1, 821.