Friendly Numbers are pairs of numbers that share a special relationship: the sum of the proper divisors of each number equals the other number. Proper divisors are the positive divisors of a number, excluding the number itself. For example, the numbers 220 and 284 are friendly because the proper divisors of 220 add up to 284, and the proper divisors of 284 add up to 220. These numbers are a fascinating topic in number theory, a branch of mathematics that studies the properties and relationships of numbers. Friendly numbers are often explored alongside other interesting concepts like amicable numbers and perfect numbers, which also involve relationships between divisors.