Why is the number 23 deficient?

Answer 1

A deficient number is one for which the sum of its factors, with the exception of itself, is less than the number itself. Or alternatively, any number for which the sum of its factors including itself is two times the number in question. As 23 is a Prime number, its only factor other than itself is 1. Another example of a deficient number close to 23 is 26 - its factors, other than itself, are 1, 2, and 13, which, added together, equals 16. The opposite of a deficient number is an abundant number.