GCF for 18 and 78

What is the Greatest Common Factor of 18 and 78?

Answer: GCF of 18 and 78 is 6

(Six)

Finding GCF for 18 and 78 using all factors (divisors) listing

The first method to find GCF for numbers 18 and 78 is to list all factors for both numbers and pick the highest common one:

All factors of 18: 1, 2, 3, 6, 9, 18

All factors of 78: 1, 2, 3, 6, 13, 26, 39, 78

So the Greatest Common Factor for 18 and 78 is 6

Finding GCF for 18 and 78 by Prime Factorization

The second method to find GCF for numbers 18 and 78 is to list all Prime Factors for both numbers and multiply the common ones:

All Prime Factors of 18: 2, 3, 3

All Prime Factors of 78: 2, 3, 13

As we can see there are Prime Factors common to both numbers: 2, 3

Now we need to multiply them to find GCF: 2 × 3 = 6

Related Calculations

GCF Table

Number 1Number 2GCF
3783
4782
5781
6786
7781
8782
9783
10782
11781
12786
137813
14782
15783
16782
17781
18786
19781
20782
21783
22782
23781
2478
25781
2678
27783
28782
29781
3078
31781
32782

About "Greatest Common Factor" Calculator

This calculator will help you find the greatest common factor (GCF) of two numbers. For example, it can help you find out what is the Greatest Common Factor of 18 and 78? (The answer is: 6). Select the first number (e.g. '18') and the second number (e.g. '78'). After that hit the 'Calculate' button.
Greatest Common Factor (GCF) also known as the Greatest Common Divisor (GCD) or Highest Common Factor (HCF) - it is the largest positive integer that divides each of the integers with zero remainder

FAQ

What is the Greatest Common Factor of 18 and 78?

GCF of 18 and 78 is 6