Is 4 a prime number?
4 is not a prime number. Here is a way to check it.
The answer
No. 4 is not a prime number: 2 × 2 = 4.
How to see that 4 is not prime
4 is in the 2 times table, so 2 is a factor as well as 1 and 4.
4 has only three factors, 1, 2 and 4: just one more than a prime has, which is still enough to rule it out.
Split 4 into prime factors
4 is 2 × 2: the same prime twice, so its factor tree stops after one split.
4 in the times tables
4 turns up in 2 different times tables, the 2 and 4: 2 × 2 and 4 × 1.
Quick checks that catch 4
- The last digit, 4, is even, so 2 goes in.
- Half of it is 2, which is still even, so 4 goes in.
4 at a glance
Optional extra number facts:
- In words
- four
- In Roman numerals
- IV
- Odd or even
- Even: it ends in 4
- Square number
- 2 × 2 = 4
- Its factors add up to
- 7, or 3 without 4 itself. 4 is deficient: Deficient means this sum is less than the number.
The numbers either side of 4
- 3 is prime: its only factors are 1 and 3. Check 3 in full
- 5 is prime: 2 does not go into it, and 3 × 3 is already past 5. Check 5 in full
Related pages
More numbers
Questions parents ask
Which prime numbers are either side of 4?
3 below it and 5 above it, a gap of 2.
What is 4 squared?
4 × 4 = 16.
What is the smallest number with as many factors as 4?
4 itself. No smaller number has 3 factors.
Continue your number practice
Explore the diagnostic for another set of practice questions.