GCF (HCF) of 9 and 21

"Greatest Common Factor" Calculator
Greatest Common Factor of
and

What is the Greatest Common Divisor of 9 and 21?

Answer

GCF (HCF) of 9 and 21 is
3

Common factors: 1, 3

3 divides both: 9 ÷ 3 = 3, 21 ÷ 3 = 7 — and 3 and 7 share no factor but 1, so no larger number divides both.

9 = 32

21 = 3 × 7

Prime921Lowest power
33233
7—7—

— = power 0: the prime is not a factor of this number, so it cannot be in the GCF.

GCF = 3

More with these numbers

Related Calculations

See Also

GCF Table

Number 1Number 2GCF
951
963
971
981
9101
9111
9123
9131
9141
9153
9161
9171
9189
9191
9201
9213
9221
9243
9251
9261
9279
9281
9291
9303
9341
9351
9369
9393
9401
9423

FAQ

What is the Greatest Common Divisor of 9 and 21?

GCF (HCF) of 9 and 21 is 3

How to find the GCF of 9 and 21?

You can find the GCF of 9 and 21 by listing all factors of both numbers and picking the greatest common one, or by prime factorization. The GCF of 9 and 21 is 3.

What prime factors do 9 and 21 share?

The prime factorizations of 9 and 21 have 3 in common, and multiplying those shared primes gives 3 — exactly the greatest common factor.

How does the GCF reduce the fraction 9/21?

Divide the numerator and the denominator by the GCF 3: 9 ÷ 3 = 3 and 21 ÷ 3 = 7. So 9/21 in lowest terms is 3/7.

See Also