Is 28 a prime number?
No, 28 is not a prime number. It is divisible by 2: 28 = 2 × 14.
Is 28 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 √28 ≈ 5.29. If none of them divides 28, it is prime.
- 3
2 divides 28 exactly, so it is not prime. Its prime factorisation is
LaTeX source of the formulas on this page
\[ 28 = 2^{2} \times 7 \]Testing 28 by the primes up to its square root
| Prime | Division | Result |
|---|---|---|
| 2 | 28 ÷ 2 | divides exactly (14) |
| 3 | 28 ÷ 3 | leaves 1 |
| 5 | 28 ÷ 5 | leaves 3 |
Questions
Is 28 a prime number?
No, 28 is not a prime number. It is divisible by 2: 28 = 2 × 14.
What is the next prime after 28?
29.
What is the prime number before 28?
23.
What are the factors of 28?
1, 2, 4, 7, 14, 28.