Prime and Composite Numbers
Prime Numbers
The mathematical definition of a prime number is a number that has exactly two factors (no more or no less). Commonly though people think of prime numbers as being those that can only be divided exactly by 1 and by the number itself.
The number 7 is not exactly divisible by any number other than 1 and 7
It has two factors only; 1 and 7
Therefore, 7 is a prime number.
In other words, prime numbers have only 2 factors.
The first five prime numbers are; 2 , 3, 5 , 7 , 11
Is 1 a Prime Number?
The number 1 has only one factor so 1 is not a prime number.
Composite Numbers
A natural number that has more than two factors is called a composite number. In other words, a composite number has factors in addition to one and itself.
- All even numbers are divisible by two and so all even numbers greater than two are composite numbers.
- All numbers that end in five are divisible by five. Therefore all numbers that end with five and are greater than five are composite numbers.
- The numbers 0 and 1 are neither prime nor composite.
- If any whole number greater than 1 is not a prime number, then it is a composite number.
Prime or Composite?
| Number | Factors (or can be exactly divided by) | Composite or Prime? |
| 2 | 1 , 2 | Prime |
| 3 | 1 , 3 | Prime |
| 4 | 1 , 2 , 4 | Composite |
| 5 | 1 , 5 | Prime |
| 6 | 1 , 2 , 3 , 6 | Composite |
| 7 | 1 , 7 | Prime |
| 8 | 1, 2 , 4 , 8 | Composite |
| 9 | 1, 3 , 9 | Composite |
| 10 | 1, 2 , 5 , 10 | Composite |
| 11 | 1, 11 | Prime |
| 12 | 1 , 2 , 3 , 6 , 12 | Composite |
| 13 | 1, 13 | Prime |
| 14 | 1, 2 , 7 , 14 | Composite |
| 15 | 1, 3 , 5 , 15 | Composite |
Try our fun Prime or Composite math game (or this other version here) and also have a go at the Factors - Prime and Composite Numbers worksheets below.
Prime/ Composite Worksheets
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