Is 63 a prime number?
63 is not a prime number. Here is a way to check it.
The answer
No. 63 is not a prime number: 3 × 21 = 63.
How to see that 63 is not prime
Its digits add up to 6 + 3 = 9, which is a multiple of 3. That means 63 is a multiple of 3 too, so 3 is a factor.
63 has 6 factors (1, 3, 7, 9, 21 and 63), which make 3 factor pairs.
Split 63 into prime factors
Split off the smallest prime each time, and keep going until every part is prime:
- 63 = 3 × 21
- 63 = 3 × 3 × 7
With repeated primes written as powers, that is 3² × 7. A small raised number tells you how many times to use that factor: for example, 2³ means 2 × 2 × 2.
63 in the times tables
63 turns up in 2 different times tables, the 7 and 9: 7 × 9 and 9 × 7.
Quick checks that catch 63
- The digits add up to 9, which is in the 3 times table, so 3 goes in.
- The digit total, 9, is a multiple of 9, so 9 goes in.
63 at a glance
Optional extra number facts:
- In words
- sixty-three
- In Roman numerals
- LXIII
- Odd or even
- Odd: it ends in 3
- Its factors add up to
- 104, or 41 without 63 itself. 63 is deficient: Deficient means this sum is less than the number.
The numbers either side of 63
- 62 is not prime. 62 is even, and every even number can be divided by 2, so 2 is a factor as well as 1 and 62. Check 62 in full
- 64 is not prime. 64 is even, and every even number can be divided by 2, so 2 is a factor as well as 1 and 64. Check 64 in full
Turn the digits round
63 backwards is 36. 36 is not prime. 36 is even, and every even number can be divided by 2, so 2 is a factor as well as 1 and 36. Check 36 in full
Related pages
More numbers
Questions parents ask
Which prime numbers are either side of 63?
61 below it and 67 above it, a gap of 6.
What is 63 squared?
63 × 63 = 3969.
What is the smallest number with as many factors as 63?
12. It has 6 factors, the same as 63.
Continue your number practice
Explore the diagnostic for another set of practice questions.