312 = 2 × 2 × 2 × 3 × 13 = 2³ × 3 × 13
divide 312 by 2 until complete then 3 then 13 to obtain prime factors
312 ÷ 2 = 156
156 ÷ 2 = 78
78 ÷ 2 = 39 ( 2 does not divide into 39 , move to next prime 3 )
39 ÷ 3 = 13
13 ÷ 13 = 1 ( on reaching 1 , completed )