Is 10 a prime number?
10 is not a prime number. Here is a way to check it.
The answer
No. 10 is not a prime number: 2 × 5 = 10.
How to see that 10 is not prime
10 is even, and every even number can be divided by 2, so 2 is a factor as well as 1 and 10.
10 has four factors: 1 and 10, plus one pair in between, 2 and 5.
Split 10 into prime factors
10 splits straight into two primes, 2 × 5, so its factor tree has only one branch.
10 in the times tables
10 turns up in 3 different times tables, the 2, 5 and 10: 2 × 5, 5 × 2 and 10 × 1.
Quick checks that catch 10
- The last digit, 0, is even, so 2 goes in.
- It ends in 0, so 5 goes in.
- It ends in 0, so 10 goes in.
10 at a glance
Optional extra number facts:
- In words
- ten
- In Roman numerals
- X
- Odd or even
- Even: it ends in 0
- Triangular number
- 1 + 2 + … + 4 = 10, a triangle of counters with 4 on the bottom row
- Multiple of 10
- 1 ten
- Its factors add up to
- 18, or 8 without 10 itself. 10 is deficient: Deficient means this sum is less than the number.
The numbers either side of 10
- 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
- 11 is prime: 2 and 3 do not go into it, and 5 × 5 is already past 11. Check 11 in full
Related pages
More numbers
Questions parents ask
Which prime numbers are either side of 10?
7 below it and 11 above it, a gap of 4.
What is 10 squared?
10 × 10 = 100.
What is the smallest number with as many factors as 10?
6. It has 4 factors, the same as 10.
Continue your number practice
Explore the diagnostic for another set of practice questions.