(In)efficiency of Factorization. Since multiplication conserves information the function is, to an extent, reversible. The process of finding the unique set of primes for a certain natural number n is called factorization. Observe that the use of the term “only” in the definition of a prime number implies that this is in fact a negative characterization: a number n is prime if there exists no number between 1 and n that divides it. This gives us an effective procedure for factorization of a number n (simply try to divide n by all numbers between 1 and \(n)\), but such techniques are not efficient.