A pseudoperfect number (http://mathworld.wolfram.com/PseudoperfectNumber.html) is a positive integer that can be written as a sum of distinct proper divisors of it.
So, to decide whether a number $n$ is pseudoperfect, we have to decide whether a subset of the set of proper divisors of $n$ has sum $n$. The subset-problem is NP-complete in general. If the number of divisors is very high, brute force will not be feasible.
Is there an efficient algorithm to decide whether $n$ is pseudoperfect , assuming that the prime factorization of $n$ is known ?