Definition:Perfect Number

Also see

 * Equivalence of Definitions of Perfect Number


 * Definition:Abundance
 * Definition:Abundancy Index


 * Definition:Deficient Number
 * Definition:Abundant Number


 * Definition:Almost Perfect Number
 * Definition:Quasiperfect Number


 * Theorem of Even Perfect Numbers: An even perfect number is of the form $2^{n-1} \left({2^n - 1}\right)$, where $2^n - 1$ is prime.


 * Are All Perfect Numbers Even?