The Highest Common Factor (HCF) of 64 and 56 is 8. To find the HCF, you can determine the factors of both numbers: 64 (1, 2, 4, 8, 16, 32, 64) and 56 (1, 2, 4, 7, 8, 14, 28, 56). The largest number that appears in both lists is 8, making it the HCF of 64 and 56.