All Divisors

List every divisor of n in ascending order in O(√n):

1. loop d from 1 while d × d ≤ n
2. when d divides n, record d in a small list and n / d in a large list (skip it when d × d = n)
3. the answer is small followed by large reversed

That gives sorted output without calling sort, because the small partners grow while their large partners shrink.