What is the Greatest Common Factor of 9 and 21?
Greatest common factor (GCF) of 9 and 21 is 3.
GCF(9,21) = 3
We will now calculate the prime factors of 9 and 21, than find the greatest common factor (greatest common divisor (gcd)) of the numbers by matching the biggest common factor of 9 and 21.
How to find the GCF of 9 and 21?
We will first find the prime factorization of 9 and 21. After we will calculate the factors of 9 and 21 and find the biggest common factor number .
Step-1: Prime Factorization of 9
Prime factors of 9 are 3. Prime factorization of 9 in exponential form is:
9 = 32
Step-2: Prime Factorization of 21
Prime factors of 21 are 3, 7. Prime factorization of 21 in exponential form is:
21 = 31 × 71
Step-3: Factors of 9
List of positive integer factors of 9 that divides 9 without a remainder.
1, 3
Step-4: Factors of 21
List of positive integer factors of 21 that divides 9 without a remainder.
1, 3, 7
Final Step: Biggest Common Factor Number
We found the factors and prime factorization of 9 and 21. The biggest common factor number is the GCF number.
So the greatest common factor 9 and 21 is 3.
Also check out the Least Common Multiple of 9 and 21