The proper factors are 1 and 3. Numbers may be designated perfect, defective, or abundant based on the sum of their proper factors. A perfect number is equal to the sum of all of its factors, except the number itself. Read the example below. There are no known odd perfect numbers.
Perfect numbers are very rare.
Abundant Numbers Abundant numbers are those numbers where the sum of the proper factors is greater than the number itself. The number 12 is the first abundant number. There are only 21 abundant numbers between 12 and 100. Defective numbers are sometimes called deficient numbers. Most numbers are defective because they have very few factors.