What is the greatest common factor of 4, 8 and 15?
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Detailed Answer:Greatest Common Divisor explained here

You have reached us maybe looking for answers to the questions like: What is the greatest common factor of 4, 8 and 15? or what is the highest common factor (HCF) of 4, 8 and 15?
What is the GCF of 4, 8 and 15?
The first step to find the gcf of 4, 8 and 15 is to list the factors of each number. The factors of 4 are 1, 2 and 4. The factors of 8 are 1, 2, 4 and 8. The factors of 15 are 1, 3, 5 and 15. So, the Greatest Common Factor for these numbers is 1 because it divides all them without a remainder. Read more about Common Factors below.
See also:
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(4,8,15).
In this case we have:
 The factors of 4 (all the whole numbers that can divide the number without a remainder) are 1, 2 and 4;
 The factors of 8 are 1, 2, 4 and 8;
 The factors of 15 are 1, 3, 5 and 15.
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 4, 8 and 15 is 1. The GCF is the largest common positive integer that divides all the numbers (4,8,15) without a remainder.
The GCF is also known as:
 Greatest common divisor (gcd);
 Highest common factor (hcf);
 Greatest common measure (gcm), or
 Highest common divisor