Category
page 1Perfect numbers
perfect number
positive integer which equals the sum of all its divisors
Mersenne prime
prime number of the form 2ⁿ−1
pseudoperfect number
positive integer that equals the sum of some of its proper divisors
multiply perfect number
number whose divisors add to a multiple of that number
Euclid–Euler theorem
theorem characterizing the even perfect numbers
aliquot sum
sum of all proper divisors of a natural number
harmonic divisor number
positive integer whose divisors have a harmonic mean that is an integer
list of Mersenne primes and perfect numbers
Wikimedia list article
hemiperfect number
number with a half-integer abundancy index
hyperperfect number
natural number n for which the equality n=1+k(σ(n)−n−1) holds for some k
unitary perfect number
integer which is the sum of its positive proper unitary divisors, not including the number itself