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

The number 1 has only one factor so **1 is not a prime number.**

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.

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.