What is the HCF of 21 77 84?

The Highest Common Factor (HCF) of 21, 77, and 84 is 7. To find the HCF, you need to identify the common factors of the numbers and determine the highest one they all share. In this case, the factors of 21 are 1, 3, 7, 21; the factors of 77 are 1, 7, 11, 77; and the factors of 84 are 1, 2, 3, 4, 6, 7, 12, 14, 21, 28, 42, 84. The highest common factor among them is 7.