To reduce power in exponentiation modulo, you need to apply the rules of modular arithmetic, or even some advanced math theorems, like Fermat's little theorem or one of its generalizations, e.g., Euler's theorem.

If the numbers at hand are not very big, you can simply solve the exponent first and then apply the modulo. Otherwise, you either need to apply some smart reasoning, a math theorem (like Fermat's little theorem or Euler's theorem), or a specialized computer algorithm that performs fast modular exponentiation.

Modular exponentiation means that we're calculating powers in modular arithmetic, that is, performing an operation of the form a^b mod n, where a, b, and n are integers. If b is negative, modular exponentiation is linked to modular multiplication inverses.