GCF for 28, 42 and 70

"Greatest Common Factor of 3 Numbers" Calculator

What's the Greatest Common Factor (GCF) of 28, 42 and 70?

Answer

GCF of 28, 42 and 70 is

(Fourteen)

14 is the largest positive integer that divides 28, 42 and 70 without a remainder — every other common divisor of the three divides it too.

Finding the GCF of 28, 42 and 70 by Prime Factorization

Split all three numbers into prime factors, then keep every prime that appears in all three of them, each taken as many times as it appears in the poorest factorization. Multiplying what is left gives the greatest common factor:

All Prime Factors of 28: 2 × 2 × 7 (exponent form: 2² × 7)

All Prime Factors of 42: 2 × 3 × 7 (exponent form: 2 × 3 × 7)

All Prime Factors of 70: 2 × 5 × 7 (exponent form: 2 × 5 × 7)

Prime factor	28	42	70	Lowest power
2	2²	2	2	2
3	—	3	—	—
5	—	—	5	—
7	7	7	7	7

GCF = 2 × 7 = 14

Checking the GCF of 28, 42 and 70 Two Numbers at a Time

The greatest common factor is associative, so three numbers can be handled as two pairs — and this is what makes the Euclidean algorithm usable here: run it on the first pair, then run it again on that result and the third number.

GCF(a, b, c) = GCF(GCF(a, b), c)

GCF(28, 42) = 14

GCF(14, 70) = 14

GCF(28, 42, 70) = 14

The answer checks out by division — all three quotients come out whole:

28 ÷ 14 = 2

42 ÷ 14 = 3

70 ÷ 14 = 5

2, 3 and 5 have no common factor left — that is what makes 14 the greatest one.

Related Calculations

About "Greatest Common Factor of 3 Numbers" Calculator

This calculator finds the Greatest Common Factor (GCF) of three numbers at once, without doing it in two passes. For example, it can help you find out what's the Greatest Common Factor (GCF) of 28, 42 and 70? (The answer is: 14). Enter the first number (e.g. '28'), the second (e.g. '42') and the third (e.g. '70'), then hit the 'Calculate' button.

The Greatest Common Factor of three numbers — also called the greatest common divisor (GCD) or highest common factor (HCF) — is the largest positive integer that divides all three of them with zero remainder

"Greatest Common Factor of 3 Numbers" Calculator

GCF Table

Number 1	Number 2	Number 3	GCF
28	42	55	1
28	42	56	14
28	42	57	1
28	42	58	2
28	42	59	1
28	42	60	2
28	42	61	1
28	42	62	2
28	42	63	7
28	42	64	2
28	42	65	1
28	42	66	2
28	42	67	1
28	42	68	2
28	42	69	1
28	42	70	14
28	42	71	1
28	42	72	2
28	42	73	1
28	42	74	2
28	42	75	1
28	42	76	2
28	42	77	7
28	42	78	2
28	42	79	1
28	42	80	2
28	42	81	1
28	42	82	2
28	42	83	1
28	42	84	14

FAQ

What's the Greatest Common Factor (GCF) of 28, 42 and 70?

GCF of 28, 42 and 70 is 14

What prime factors do 28, 42 and 70 share?

All three factorizations contain 2 × 7, and multiplying those shared primes gives 14 — exactly the greatest common factor.

Can you get the GCF of 28, 42 and 70 two numbers at a time?

Yes, and it is the check this page prints. The GCF of 28 and 42 is 14, and the GCF of 14 and 70 is 14 — the same answer, because the greatest common factor is associative and does not depend on the order of the three numbers.

How does the GCF simplify the ratio 28 : 42 : 70?

Divide every term by the GCF 14: 28 ÷ 14 = 2, 42 ÷ 14 = 3 and 70 ÷ 14 = 5. So 28 : 42 : 70 in lowest terms is 2 : 3 : 5, and no whole number other than 1 divides all three of those.

GCF for 28, 42 and 70

What's the Greatest Common Factor (GCF) of 28, 42 and 70?

Finding the GCF of 28, 42 and 70 by Prime Factorization

Checking the GCF of 28, 42 and 70 Two Numbers at a Time

Related Calculations

See Also

About "Greatest Common Factor of 3 Numbers" Calculator

GCF Table

FAQ

What's the Greatest Common Factor (GCF) of 28, 42 and 70?

What prime factors do 28, 42 and 70 share?

Can you get the GCF of 28, 42 and 70 two numbers at a time?

How does the GCF simplify the ratio 28 : 42 : 70?

See Also

Number 1	Number 2	Number 3	GCF
28	42	55	1
28	42	56	14
28	42	57	1
28	42	58	2
28	42	59	1
28	42	60	2
28	42	61	1
28	42	62	2
28	42	63	7
28	42	64	2
28	42	65	1
28	42	66	2
28	42	67	1
28	42	68	2
28	42	69	1
28	42	70	14
28	42	71	1
28	42	72	2
28	42	73	1
28	42	74	2
28	42	75	1
28	42	76	2
28	42	77	7
28	42	78	2
28	42	79	1
28	42	80	2
28	42	81	1
28	42	82	2
28	42	83	1
28	42	84	14

Number 1	Number 2	Number 3	GCF
28	42	55	1
28	42	56	14
28	42	57	1
28	42	58	2
28	42	59	1
28	42	60	2
28	42	61	1
28	42	62	2
28	42	63	7
28	42	64	2
28	42	65	1
28	42	66	2
28	42	67	1
28	42	68	2
28	42	69	1
28	42	70	14
28	42	71	1
28	42	72	2
28	42	73	1
28	42	74	2
28	42	75	1
28	42	76	2
28	42	77	7
28	42	78	2
28	42	79	1
28	42	80	2
28	42	81	1
28	42	82	2
28	42	83	1
28	42	84	14

Number 1	Number 2	Number 3	GCF
28	42	55	1
28	42	56	14
28	42	57	1
28	42	58	2
28	42	59	1
28	42	60	2
28	42	61	1
28	42	62	2
28	42	63	7
28	42	64	2
28	42	65	1
28	42	66	2
28	42	67	1
28	42	68	2
28	42	69	1
28	42	70	14
28	42	71	1
28	42	72	2
28	42	73	1
28	42	74	2
28	42	75	1
28	42	76	2
28	42	77	7
28	42	78	2
28	42	79	1
28	42	80	2
28	42	81	1
28	42	82	2
28	42	83	1
28	42	84	14