What is the GCF of 12, 18 and 21?

What's the Greatest Common Factor (GCF) of 12, 18 and 21?

Answer

GCF of 12, 18 and 21 is

3

Common factors: 1, 3

3 divides all three: 12 ÷ 3 = 4, 18 ÷ 3 = 6, 21 ÷ 3 = 7 — and 4, 6 and 7 have no factor but 1 common to all of them, so no larger number divides all three.

12 = 2² × 3

18 = 2 × 3²

21 = 3 × 7

Prime	12	18	21	Lowest power
2	2²	2	—	—
3	3	3²	3	3
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

GCF Table

1st	2nd	3rd	GCF
6	12	18	6
7	12	18	1
8	12	18	2
9	12	18	3
10	12	18	2
11	12	18	1
12	12	18	6
12	13	18	1
12	14	18	2
12	15	18	3
12	16	18	2
12	17	18	1
12	18	18	6
12	18	19	1
12	18	20	2
12	18	21	3
12	18	22	2
12	18	23	1
12	18	24	6
12	18	25	1
12	18	26	2
12	18	27	3
12	18	28	2
12	18	29	1
12	18	30	6
12	18	31	1
12	18	32	2
12	18	33	3
12	18	34	2
12	18	35	1

GCF for 12, 18 and 21

What's the Greatest Common Factor (GCF) of 12, 18 and 21?

More with these numbers

Related Calculations

See Also

GCF Table

FAQ

What's the Greatest Common Factor (GCF) of 12, 18 and 21?

What prime factors do 12, 18 and 21 share?

Can you get the GCF of 12, 18 and 21 two numbers at a time?

How does the GCF simplify the ratio 12 : 18 : 21?

See Also

1st	2nd	3rd	GCF
6	12	18	6
7	12	18	1
8	12	18	2
9	12	18	3
10	12	18	2
11	12	18	1
12	12	18	6
12	13	18	1
12	14	18	2
12	15	18	3
12	16	18	2
12	17	18	1
12	18	18	6
12	18	19	1
12	18	20	2
12	18	21	3
12	18	22	2
12	18	23	1
12	18	24	6
12	18	25	1
12	18	26	2
12	18	27	3
12	18	28	2
12	18	29	1
12	18	30	6
12	18	31	1
12	18	32	2
12	18	33	3
12	18	34	2
12	18	35	1

1st	2nd	3rd	GCF
6	12	18	6
7	12	18	1
8	12	18	2
9	12	18	3
10	12	18	2
11	12	18	1
12	12	18	6
12	13	18	1
12	14	18	2
12	15	18	3
12	16	18	2
12	17	18	1
12	18	18	6
12	18	19	1
12	18	20	2
12	18	21	3
12	18	22	2
12	18	23	1
12	18	24	6
12	18	25	1
12	18	26	2
12	18	27	3
12	18	28	2
12	18	29	1
12	18	30	6
12	18	31	1
12	18	32	2
12	18	33	3
12	18	34	2
12	18	35	1

1st	2nd	3rd	GCF
6	12	18	6
7	12	18	1
8	12	18	2
9	12	18	3
10	12	18	2
11	12	18	1
12	12	18	6
12	13	18	1
12	14	18	2
12	15	18	3
12	16	18	2
12	17	18	1
12	18	18	6
12	18	19	1
12	18	20	2
12	18	21	3
12	18	22	2
12	18	23	1
12	18	24	6
12	18	25	1
12	18	26	2
12	18	27	3
12	18	28	2
12	18	29	1
12	18	30	6
12	18	31	1
12	18	32	2
12	18	33	3
12	18	34	2
12	18	35	1