Is 13 a prime number?
13 is a prime number. Here is how to check it, one division at a time.
The answer
Yes. 13 is a prime number: its only factors are 1 and 13.
How to check that 13 is prime
Try dividing 13 by the prime numbers, starting with 2. You only need primes: if 4 went into 13, then 2 would too.
- 13 ÷ 2 = 6 remainder 1, so 2 is not a factor.
- 13 ÷ 3 = 4 remainder 1, so 3 is not a factor.
Stop at 5: 5 × 5 = 25, which is more than 13. Any factor bigger than that would need a partner smaller than 5, and you have already tried those. So 13 is prime.
Where 13 comes among the primes
13 is the 6th prime number. The prime just before it is 11.
There are 25 prime numbers up to 100: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89 and 97.
Around 13
- 13 is not in any times table from 2 to 12. The answers either side of it are 12 (2 × 6, 3 × 4, 4 × 3, 6 × 2 and 12 × 1) and 14 (2 × 7 and 7 × 2).
- The nearest square number is 16 (4 × 4), 3 above it.
- Two prime numbers with a difference of 4 are called cousin primes. 13 has one cousin prime: 17.
13 at a glance
Optional extra number facts:
- In words
- thirteen
- In Roman numerals
- XIII
- Odd or even
- Odd: it ends in 3
- Its factors add up to
- 14, or 1 without 13 itself. 13 is deficient: Deficient means this sum is less than the number.
Related pages
More numbers
Questions parents ask
Is 13 one of a pair of twin primes?
Yes. Twin primes are two primes 2 apart, and 13 pairs with 11.
What is the next prime number after 13?
17, which is 4 more than 13. Every number in between has a factor other than 1 and itself.
What is 13 × 13?
13 × 13 = 169. The square of a prime has exactly three factors: 1, 13 and 169.
Continue your number practice
Explore the diagnostic for another set of practice questions.