What is the Highest Common Factor of 42, 168 and 210?

14 21 42 7

42

42 = 2 x 3 x 7 168 = 2 x 2 x 2 x 3 x 7 210 = 2 x 3 x 5 x 7 So,  the Highest Common Factor of 42, 168 and 210 = 2 x 3 x 7 = 42