The expression a^(p-1) is often encountered in number theory, particularly in relation to Fermat's Little Theorem. This theorem states that if p is a prime number and a is an integer not divisible by p , then a^(p-1) \equiv 1 \mod p . This means that when a^(p-1) is divided by p , the remainder is 1. In simpler terms, a^(p-1) represents the result of raising the number a to the power of one less than the prime p . This concept is crucial in fields like cryptography and computer science, where modular arithmetic plays a significant role in securing data and ensuring efficient algorithms.