Is 840 a prime number?
No, 840 is not a prime number. It is divisible by 2: 840 = 2 × 420.
Is 840 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 √840 ≈ 28.98. If none of them divides 840, it is prime.
- 3
2 divides 840 exactly, so it is not prime. Its prime factorisation is
LaTeX source of the formulas on this page
\[ 840 = 2^{3} \times 3 \times 5 \times 7 \]Testing 840 by the primes up to its square root
| Prime | Division | Result |
|---|---|---|
| 2 | 840 ÷ 2 | divides exactly (420) |
| 3 | 840 ÷ 3 | divides exactly (280) |
| 5 | 840 ÷ 5 | divides exactly (168) |
| 7 | 840 ÷ 7 | divides exactly (120) |
| 11 | 840 ÷ 11 | leaves 4 |
| 13 | 840 ÷ 13 | leaves 8 |
| 17 | 840 ÷ 17 | leaves 7 |
| 19 | 840 ÷ 19 | leaves 4 |
| 23 | 840 ÷ 23 | leaves 12 |
Questions
Is 840 a prime number?
No, 840 is not a prime number. It is divisible by 2: 840 = 2 × 420.
What is the next prime after 840?
853.
What is the prime number before 840?
839.
What are the factors of 840?
1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 14, 15, 20, 21, 24, 28, 30, 35, 40, 42, 56, 60, 70, 84, 105, 120, 140, 168, 210, 280, 420, 840.