Greatest Common Factor Calculator
Greatest Common Factor Calculator / Converter
Enter values separeted by commas: Ex.: 2,4,8, etc. 
Detailed Answer:Greatest Common Divisor explained here

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Use our Greatest Common Factor to find the GCF of any combination of numbers.
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How to find the Greatest Common Factor
GCF example:
The first step is to find all divisors of each number. For instance, let us find the gcf(84,89,36).
In this case we have:
 The factors of 84 (all the whole numbers that can divide the number without a remainder) are 1, 2, 3, 4, 6, 7, 12, 14, 21, 28, 42 and 84;
 The factors of 89 are 1 and 89;
 The factors of 36 are 1, 2, 3, 4, 6, 9, 12, 18 and 36.
The second step is to analyze which are the common divisors. It is not difficult to see that the 'Greatest Common Factor' or 'Divisor' for 84, 89 and 36 is 1. The GCF is the largest common positive integer that divides all the numbers (84,89,36) without a remainder.
In the name greatest common divisor, the adjective "greatest" may be replaced by "highest", and the word "divisor" may be replaced by "factor", so that other names include highest common factor (hcf), greatest common measure, among others.
So, the GCF is also known as:
 Greatest common divisor (gcd);
 Highest common factor (hcf);
 Greatest common measure (gcm), or
 Highest common divisor