What is the greatest common factor of 20 and 8?

The greatest common factor (GCF) of 20 and 8 is 4. This is because 4 is the largest positive integer that divides both 20 and 8 without leaving a remainder. The prime factorization of 20 is 2^2 × 5, while the prime factorization of 8 is 2^3. To find the GCF, we need to identify the highest power of each prime factor that is common to both numbers, which in this case is 2^2 or 4. Therefore, the GCF of 20 and 8 is 4.