Is 8 a prime number?
8 is not a prime number. Here is a way to check it.
The answer
No. 8 is not a prime number: 2 × 4 = 8.
How to see that 8 is not prime
8 is in the 2 times table, so 2 is a factor as well as 1 and 8.
8 has four factors: 1 and 8, plus one pair in between, 2 and 4.
Split 8 into prime factors
Split off the smallest prime each time, and keep going until every part is prime:
- 8 = 2 × 4
- 8 = 2 × 2 × 2
With repeated primes written as powers, that is 2³. A small raised number tells you how many times to use that factor: for example, 2³ means 2 × 2 × 2.
8 in the times tables
8 turns up in 3 different times tables, the 2, 4 and 8: 2 × 4, 4 × 2 and 8 × 1.
Quick checks that catch 8
- The last digit, 8, is even, so 2 goes in.
- Half of it is 4, which is still even, so 4 goes in.
8 at a glance
Optional extra number facts:
- In words
- eight
- In Roman numerals
- VIII
- Odd or even
- Even: it ends in 8
- Cube number
- 2 × 2 × 2 = 8
- Its factors add up to
- 15, or 7 without 8 itself. 8 is deficient: Deficient means this sum is less than the number.
The numbers either side of 8
- 7 is prime: 2 does not go into it, and 3 × 3 is already past 7. Check 7 in full
- 9 is not prime. 9 is in the 3 times table, so 3 is a factor as well as 1 and 9. Check 9 in full
Related pages
More numbers
Questions parents ask
Which prime numbers are either side of 8?
7 below it and 11 above it, a gap of 4.
What is 8 squared?
8 × 8 = 64.
What is the smallest number with as many factors as 8?
6. It has 4 factors, the same as 8.
Continue your number practice
Explore the diagnostic for another set of practice questions.