# Calculate the Greatest Common Factor or GCF of 686

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The instructions to find the GCF of 686 are the next:

## 1. Decompose all numbers into prime factors

686 | 2 |

343 | 7 |

49 | 7 |

7 | 7 |

1 |

## 2. Write all numbers as the product of its prime factors

Prime factors of 686 | = | 2 . 7^{3} |

## 3. Choose the common prime factors with the lowest exponent

Common prime factors: 2 , 7

Common prime factors with the lowest exponent: 2^{1}, 7^{3}

## 4. Calculate the Greatest Common Factor or GCF

Remember, to find the GCF of several numbers you must multiply the common prime factors with the lowest exponent.

**GCF** = 2^{1}. 7^{3} = 686

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