Can you give an equation or relationship in mathematical form?
I tried to express this as a congruence (inverse modulo), i'm not sure it is right, but it seems to be:
for any integer m
and thus satisfying the following:
I can give you a computer procedure (algorithm) to solve it. It best works out using divisions. (If needed, take "large integers package" like BigInteger from Java or something). Keep dividing c by m, until you get a fraction, or c, or a positive number less than c. Of these outcomes, getting c means, it is a power, other outcomes prove that it is not.