GCF for 28 and 91

What is the Greatest common Divisor of 28 and 91?

Answer: GCF of 28 and 91 is 7

(Seven)

Finding GCF for 28 and 91 using all factors (divisors) listing

The first method to find GCF for numbers 28 and 91 is to list all factors for both numbers and pick the highest common one:

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

All factors of 91: 1, 7, 13, 91

So the Greatest Common Factor for 28 and 91 is 7

Finding GCF for 28 and 91 by Prime Factorization

The second method to find GCF for numbers 28 and 91 is to list all Prime Factors for both numbers and multiply the common ones:

All Prime Factors of 28: 2, 2, 7

All Prime Factors of 91: 7, 13

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 28 and 91

See Also

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 28 and 91? (The answer is: 7). Select the first number (e.g. '28') and the second number (e.g. '91'). 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

GCF Table

Number 1Number 2GCF
1391
1491
15911
16911
17911
18911
19911
20911
2191
22911
23911
2491
25911
2691
27911
2891
29911
30911
31911
32911
33911
34911
3591
36911
37911
38911
3991
40911
41911
4291

FAQ

What is the Greatest common Divisor of 28 and 91?

GCF of 28 and 91 is 7