**Factors** are numbers that equal a given number when multiplied together.

The factors of 20 are 1, 2, 4, 5, 10, and 20 because:

1 × 20 | = | 20 |

2 × 10 | = | 20 |

4 × 5 | = | 20 |

The

**greatest common factor** is the greatest factor

that two or more numbers have in common.

First, find the factors of 56 and 84.

56: | | 1, 2, 4, 7, 8, 14, 28, 56 |

84: | | 1, 2, 3, 4, 6, 7, 12, 14, 21, 28, 42, 84 |

The common factors of 56 and 84 are 1, 2, 4, 7, 14, and 28.

So, the greatest common factor of 56 and 84 is 28.