GCF for 20 and 645
"Greatest Common Factor" Calculator
What is the Greatest common Divisor of 20 and 645?
Answer: GCF of 20 and 645 is 5
(Five)
Finding GCF for 20 and 645 using all factors (divisors) listing
The first method to find GCF for numbers 20 and 645 is to list all factors for both numbers and pick the highest common one:
All factors of 20: 1, 2, 4, 5, 10, 20
All factors of 645: 1, 3, 5, 15, 43, 129, 215, 645
So the Greatest Common Factor for 20 and 645 is 5
Finding GCF for 20 and 645 by Prime Factorization
The second method to find GCF for numbers 20 and 645 is to list all Prime Factors for both numbers and multiply the common ones:
All Prime Factors of 20: 2, 2, 5
All Prime Factors of 645: 3, 5, 43
As we can see there is only one Prime Factor common to both numbers. It is 5
So 5 is the Greatest Common Factor of 20 and 645
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GCF Table
| Number 1 | Number 2 | GCF |
|---|---|---|
| 5 | 645 | 5 |
| 6 | 645 | 3 |
| 7 | 645 | 1 |
| 8 | 645 | 1 |
| 9 | 645 | 3 |
| 10 | 645 | 5 |
| 11 | 645 | 1 |
| 12 | 645 | 3 |
| 13 | 645 | 1 |
| 14 | 645 | 1 |
| 15 | 645 | 15 |
| 16 | 645 | 1 |
| 17 | 645 | 1 |
| 18 | 645 | 3 |
| 19 | 645 | 1 |
| 20 | 645 | 5 |
| 21 | 645 | 3 |
| 22 | 645 | 1 |
| 23 | 645 | 1 |
| 24 | 645 | 3 |
| 25 | 645 | 5 |
| 26 | 645 | 1 |
| 27 | 645 | 3 |
| 28 | 645 | 1 |
| 29 | 645 | 1 |
| 30 | 645 | 15 |
| 31 | 645 | 1 |
| 32 | 645 | 1 |
| 33 | 645 | 3 |
| 34 | 645 | 1 |
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 Divisor of 20 and 645? (The answer is: 5). Select the first number (e.g. '20') and the second number (e.g. '645'). 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