Is 42 a prime number?
42 is not a prime number. Here is a way to check it.
The answer
No. 42 is not a prime number: 2 × 21 = 42.
How to see that 42 is not prime
42 is even, and every even number can be divided by 2, so 2 is a factor as well as 1 and 42.
42 has 8 factors (1, 2, 3, 6, 7, 14, 21 and 42), which make 4 factor pairs.
Split 42 into prime factors
Split off the smallest prime each time, and keep going until every part is prime:
- 42 = 2 × 21
- 42 = 2 × 3 × 7
42 in the times tables
42 turns up in 2 different times tables, the 6 and 7: 6 × 7 and 7 × 6.
Quick checks that catch 42
- The last digit, 2, is even, so 2 goes in.
- The digits add up to 6, which is in the 3 times table, so 3 goes in.
- It is even and passes the check for 3 as well, so 6 goes in.
42 at a glance
Optional extra number facts:
- In words
- forty-two
- In Roman numerals
- XLII
- Odd or even
- Even: it ends in 2
- Its factors add up to
- 96, or 54 without 42 itself. 42 is abundant: Abundant means this sum is greater than the number.
The numbers either side of 42
- 41 is prime: 2, 3 and 5 do not go into it, and 7 × 7 is already past 41. Check 41 in full
- 43 is prime: 2, 3 and 5 do not go into it, and 7 × 7 is already past 43. Check 43 in full
Turn the digits round
42 backwards is 24. 24 is not prime. 24 is even, and every even number can be divided by 2, so 2 is a factor as well as 1 and 24. Check 24 in full
Related pages
More numbers
Questions parents ask
Which prime numbers are either side of 42?
41 below it and 43 above it, a gap of 2.
What is 42 squared?
42 × 42 = 1764.
What is the smallest number with as many factors as 42?
24. It has 8 factors, the same as 42.
Continue your number practice
Explore the diagnostic for another set of practice questions.