Is 15 a prime number?
No, 15 is not a prime number. It is divisible by 3: 15 = 3 × 5.
Is 15 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 √15 ≈ 3.87. If none of them divides 15, it is prime.
- 3
3 divides 15 exactly, so it is not prime. Its prime factorisation is
LaTeX source of the formulas on this page
\[ 15 = 3 \times 5 \]
Testing 15 by the primes up to its square root
| Prime | Division | Result |
|---|---|---|
| 2 | 15 ÷ 2 | leaves 1 |
| 3 | 15 ÷ 3 | divides exactly (5) |
Questions
Is 15 a prime number?
No, 15 is not a prime number. It is divisible by 3: 15 = 3 × 5.
What is the next prime after 15?
17.
What is the prime number before 15?
13.
What are the factors of 15?
1, 3, 5, 15.