Is 19 a prime number?
19 is a prime number. Here is how to check it, one division at a time.
The answer
Yes. 19 is a prime number: its only factors are 1 and 19.
How to check that 19 is prime
Try dividing 19 by the prime numbers, starting with 2. You only need primes: if 4 went into 19, then 2 would too.
- 19 ÷ 2 = 9 remainder 1, so 2 is not a factor.
- 19 ÷ 3 = 6 remainder 1, so 3 is not a factor.
Stop at 5: 5 × 5 = 25, which is more than 19. Any factor bigger than that would need a partner smaller than 5, and you have already tried those. So 19 is prime.
Where 19 comes among the primes
19 is the 8th prime number. The prime just before it is 17.
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 19
- 19 is not in any times table from 2 to 12. The answers either side of it are 18 (2 × 9, 3 × 6, 6 × 3 and 9 × 2) and 20 (2 × 10, 4 × 5, 5 × 4 and 10 × 2).
- The nearest square number is 16 (4 × 4), 3 below it.
- Two prime numbers with a difference of 4 are called cousin primes. 19 has one cousin prime: 23.
19 at a glance
Optional extra number facts:
- In words
- nineteen
- In Roman numerals
- XIX
- Odd or even
- Odd: it ends in 9
- Its factors add up to
- 20, or 1 without 19 itself. 19 is deficient: Deficient means this sum is less than the number.
Related pages
More numbers
Questions parents ask
Is 19 one of a pair of twin primes?
Yes. Twin primes are two primes 2 apart, and 19 pairs with 17.
What is the next prime number after 19?
23, which is 4 more than 19. Every number in between has a factor other than 1 and itself.
What is 19 × 19?
19 × 19 = 361. The square of a prime has exactly three factors: 1, 19 and 361.
Continue your number practice
Explore the diagnostic for another set of practice questions.