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 Description  
 Deficient Number:  A number in which the sum of all its proper divisors is less than the number itself.
The word deficient means to lack in some way. A deficient number is lacking in the sense that the sum of its proper divisors (all its positive divisors excluding itself) is less than the number itself. For example, 9 is a deficient number because the sum of its proper divisors is 1 + 3 = 4, and 4 is less than 9.