Deficient number

A deficient number is when a number is not a perfect number or an abundant number. Also all primes, as well as some prime powers, and any divisors of a perfect or deficient number are deficient. 1 is deficient along with  2, 3, 4, 5, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 19, 21, 22, 23, etc.

References

Category:Integer sequences