GCF for 21 and 28

"Greatest Common Factor" Calculator

Greatest Common Factor of

and

What is the Greatest common Divisor of 21 and 28?

Answer: GCF of 21 and 28 is 7

(Seven)

Finding GCF for 21 and 28 using all factors (divisors) listing

The first method to find GCF for numbers 21 and 28 is to list all factors for both numbers and pick the highest common one:

All factors of 21: 1, 3, 7, 21

All factors of 28: 1, 2, 4, 7, 14, 28

So the Greatest Common Factor for 21 and 28 is 7

Finding GCF for 21 and 28 by Prime Factorization

The second method to find GCF for numbers 21 and 28 is to list all Prime Factors for both numbers and multiply the common ones:

All Prime Factors of 21: 3, 7

All Prime Factors of 28: 2, 2, 7

As we can see there is only one Prime Factor common to both numbers. It is 7

So 7 is the Greatest Common Factor of 21 and 28

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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 21 and 28? (The answer is: 7). Select the first number (e.g. '21') and the second number (e.g. '28'). 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

"Greatest Common Factor" Calculator

Greatest Common Factor of

and

GCF Table

Number 1Number 2GCF
6282
7287
8284
9281
10282
11281
12284
13281
142814
15281
16284
17281
18282
19281
20284
21287
22282
23281
24284
25281
26282
27281
282828
29281
30282
31281
32284
33281
34282
35287

FAQ

What is the Greatest common Divisor of 21 and 28?

GCF of 21 and 28 is 7

See Also