if you know the number is a factorial for example 9! = 9 × 8 × 7 × 6 × 5 × 4 × 3 × 2 × 1 you have are half way of having prime factorization, you can just

if you know the number is a factorial for example 9! = 9 × 8 × 7 × 6 × 5 × 4 × 3 × 2 × 1 you have are half way of having prime factorization, you can just to compute the prime factor from 1 to 9 and you get 9! = 3^2 x 2^3 x 7 x 3 x 2 x 5 x 2^2 x 3 x 2 x1