GCF for 21 and 27

What is the Greatest Common Factor of 21 and 27?

Answer: GCF of 21 and 27 is 3

(Three)

Finding GCF for 21 and 27 using all factors (divisors) listing

The first method to find GCF for numbers 21 and 27 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 27: 1, 3, 9, 27

So the Greatest Common Factor for 21 and 27 is 3

Finding GCF for 21 and 27 by Prime Factorization

The second method to find GCF for numbers 21 and 27 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 27: 3, 3, 3

As we can see there is only one Prime Factor common to both numbers. It is 3

So 3 is the Greatest Common Factor of 21 and 27

GCF Table

Number 1Number 2GCF
627
7271
827
927
10271
11271
1227
13271
1427
1527
1627
17271
1827
1927
2027
2127
2227
23271
2427
25271
2627
272727
28271
29271
30273
31271
32271
33273
34271
35271

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 21 and 27? (The answer is: 3). Select the first number (e.g. '21') and the second number (e.g. '27'). 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 21 and 27?

GCF of 21 and 27 is 3