Make use of GCF Calculator to quickly find the Greatest Common Factor of numbers 18, 42 i.e. 6 largest integer by which both the numbers can be divided.

Greatest common factor (GCF) of 18 and 42 is **6**.

GCF(18,42) = 6

*Greatest common factor* or Greatest common divisor (GCD) can be calculated in following way;

- Greatest Common Factor of 18 and 42 by prime factorization method
- Greatest Common Factor of 18 and 42 by matching factors method

**Prime Factorization of 42**

2 | 42 |

3 | 21 |

7 | 7 |

1 |

Prime factors of 42 are 2,3,7. Prime factorization of **42** in exponential form is:

42 = 2^{1}×3^{1}×7^{1}

**Prime Factorization of 18**

2 | 18 |

3 | 9 |

3 | 3 |

1 |

Prime factors of 18 are 2,3. Prime factorization of **18** in exponential form is:

18 = 2^{1}×3^{2}

∴ So by taking common prime factors GCF of 42 and 18 is 6

**Factors of 42**

List of positive integer factors of 42 that divides 42 without a remainder.

1,2,3,6,7,14,21,42

**Factors of 18**

List of positive integer factors of 18 that divides 18 without a remainder.

1,2,3,6,9,18

**Greatest Common Factor**

We found the factors and prime factorization of 42 and 18. The biggest common factor number is the **GCF** number.

So the **greatest common factor 42 and 18** is **6**.

Also check out the Least Common Multiple of 42 and 18

(i) The GCF of 42 and 18 is associative

GCF of 42 and 18 = GCF of 18 and 42

1. What is the GCF of 42 and 18?

Answer: GCF of 42 and 18 is 6.

2. What are the Factors of 42?

Answer: Factors of 42 are 1, 2, 3, 6, 7, 14, 21, 42. There are 8 integers that are factors of 42. The greatest factor of 42 is 42.

3. What are the Factors of 18?

Answer: Factors of 18 are 1, 2, 3, 6, 9, 18. There are 6 integers that are factors of 18. The greatest factor of 18 is 18.

4. How to Find the GCF of 42 and 18?

Answer:

Greatest Common Factor of 42 and 18 = 6

Step 1: Find the prime factorization of 42

42 = 2 x 3 x 7

Step 2: Find the prime factorization of 18

18 = 2 x 3 x 3

Step 3: Multiply those factors both numbers have in common in steps i) or ii) above to find the gcf:

GCF = 2 x 3 = 6

Step 4: Therefore, the greatest common factor of 42 and 18 is 6