Is 68 a prime number?
68 is not a prime number. Here is the quickest way to see it.
The answer
No. 68 is not a prime number: 2 × 34 = 68.
How to see that 68 is not prime
68 is even, and every even number can be divided by 2, so 2 is a factor as well as 1 and 68.
68 has 6 factors (1, 2, 4, 17, 34 and 68), which make 3 factor pairs.
Split 68 into prime factors
Split off the smallest prime each time, and keep going until every part is prime:
- 68 = 2 × 34
- 68 = 2 × 2 × 17
With the repeated primes written as powers, that is 2² × 17.
68 in the times tables
No fact from the 2 to 12 times tables, up to × 12, makes 68. Its smallest pair, 2 × 34, needs the 34 times table, which goes past 12.
Quick checks that catch 68
- The last digit, 8, is even, so 2 goes in.
- Half of it is 34, which is still even, so 4 goes in.
68 at a glance
- In words
- sixty-eight
- In Roman numerals
- LXVIII
- Odd or even
- Even: it ends in 8
- Its factors add up to
- 126, or 58 without 68 itself, which makes 68 a deficient number
The numbers either side of 68
- 67 is prime: 2, 3, 5 and 7 do not go into it, and 11 × 11 is already past 67. Check 67 in full
- 69 is not prime. Its digits add up to 6 + 9 = 15, which is a multiple of 3. That means 69 is a multiple of 3 too, so 3 is a factor. Check 69 in full
Turn the digits round
68 backwards is 86. 86 is not prime. 86 is even, and every even number can be divided by 2, so 2 is a factor as well as 1 and 86. Check 86 in full
Related pages
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Questions parents ask
Which prime numbers are either side of 68?
67 below it and 71 above it, a gap of 4.
What is 68 squared?
68 × 68 = 4624.
What is the smallest number with as many factors as 68?
12. It has 6 factors, the same as 68.
Number facts are the base of 11+ maths
Factors, multiples, primes and square numbers come up all over 11+ maths, from simplifying fractions to ratio. The free diagnostic checks maths, English and both kinds of reasoning, and shows what to practise next. No card is required.