Perfect, Abundant, and Deficient Numbers

Numbers can be classified based on the sum of their proper divisors (divisors excluding the number itself).

• A perfect number has a sum of proper divisors equal to itself. The first few are 6, 28, and 496.
• An abundant number has a sum of proper divisors greater than itself. For example, the proper divisors of 12 are 1, 2, 3, 4, and 6, which sum to 16. Any multiple of a perfect or abundant number is also abundant.
• A deficient number has a sum of proper divisors less than itself. All prime numbers are deficient.