a) 720 = 2 × 2 × 2 × 2 × 3 × 3 × 5
б) 1845 = 3 × 3 × 3 × 5 × 17
в) 999 = 3 × 3 × 3 × 37
г) 3618 = 2 × 3 × 3 × 3 × 67