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    GCF of 21 and 42 (Greatest Common Factor)

    "Greatest Common Factor" Calculator

    Greatest Common Factor of

    and

    What is the Greatest Common Divisor of 21 and 42?

    Answer

    GCF of 21 and 42 is
    21

    (Twenty-one)

    Finding GCF for 21 and 42 using all factors (divisors) listing

    The first method to find GCF for numbers 21 and 42 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 42: 1, 2, 3, 6, 7, 14, 21, 42

    So the Greatest Common Factor for 21 and 42 is 21

    Finding GCF for 21 and 42 by Prime Factorization

    The second method to find GCF for numbers 21 and 42 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 42: 2, 3, 7

    As we can see there are Prime Factors common to both numbers: 3, 7

    Now we need to multiply them to find GCF: 3 × 7 = 21

    Related Calculations

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    What is the GCF of 21 and 42. The GCF of 21 and 42 is 21 — the biggest number that can divide both integers. Step-by-step GCF (GCD) calculation by factoring.
    https://calculat.io/en/number/greatest-common-factor-of/21--42/generated.jpgCopy

    GCF Table

    Number 1Number 2GCF
    21153
    21221
    21243
    21251
    21261
    21273
    21287
    21303
    21321
    21333
    21357
    21363
    21371
    21381
    21393
    21401
    214221
    21441
    21453
    21461
    21483
    21497
    21501
    21513
    21543
    21567
    21603
    21707
    218421

    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 Divisor of 21 and 42? (The answer is: 21). Select the first number (e.g. '21') and the second number (e.g. '42'). 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.
    "Greatest Common Factor" Calculator

    Greatest Common Factor of

    and

    FAQ

    What is the Greatest Common Divisor of 21 and 42?

    GCF of 21 and 42 is 21

    How to find the GCF of 21 and 42?

    You can find the GCF of 21 and 42 by listing all factors of both numbers and picking the greatest common one, or by prime factorization. The GCF of 21 and 42 is 21.

    What prime factors do 21 and 42 share?

    The prime factorizations of 21 and 42 have 3 × 7 in common, and multiplying those shared primes gives 21 — exactly the greatest common factor.

    How does the GCF reduce the fraction 21/42?

    Divide the numerator and the denominator by the GCF 21: 21 ÷ 21 = 1 and 42 ÷ 21 = 2. So 21/42 in lowest terms is 1/2.

    See Also