Is 17 a prime number?
17 is a prime number. Here is how to check it, one division at a time.
The answer
Yes. 17 is a prime number: its only factors are 1 and 17.
How to check that 17 is prime
Try dividing 17 by the prime numbers, starting with 2. You only need primes: if 4 went into 17, then 2 would too.
- 17 ÷ 2 = 8 remainder 1, so 2 is not a factor.
- 17 ÷ 3 = 5 remainder 2, so 3 is not a factor.
Stop at 5: 5 × 5 = 25, which is more than 17. Any factor bigger than that would need a partner smaller than 5, and you have already tried those. So 17 is prime.
Where 17 comes among the primes
17 is the 7th prime number. The prime just before it is 13.
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 17
- 17 is not in any times table from 2 to 12. The answers either side of it are 16 (2 × 8, 4 × 4 and 8 × 2) and 18 (2 × 9, 3 × 6, 6 × 3 and 9 × 2).
- The nearest square number is 16 (4 × 4), 1 below it.
- Two prime numbers with a difference of 4 are called cousin primes. 17 has one cousin prime: 13.
17 at a glance
Optional extra number facts:
- In words
- seventeen
- In Roman numerals
- XVII
- Odd or even
- Odd: it ends in 7
- Its factors add up to
- 18, or 1 without 17 itself. 17 is deficient: Deficient means this sum is less than the number.
Related pages
More numbers
Questions parents ask
Is 17 one of a pair of twin primes?
Yes. Twin primes are two primes 2 apart, and 17 pairs with 19.
What is the next prime number after 17?
19, which is 2 more than 17. Every number in between has a factor other than 1 and itself.
What is 17 × 17?
17 × 17 = 289. The square of a prime has exactly three factors: 1, 17 and 289.
Continue your number practice
Explore the diagnostic for another set of practice questions.