Divisor function

positive integer which equals the sum of all its divisors

pair of integers related by their divisors

number for which the sum of its proper divisors is greater than the number itself

natural integer number for which the sum of its proper strict divisors (other than itself) is less than the number itself

numbers whose aliquot sums form a cyclic sequence

arithmetic function related to the divisors of an integer

hypothetical number whose sum of divisors is twice the number plus 1

abundant number that is not semiperfect

Numbers divisible by another number

positive integer unexpressable as the sum of all proper divisors of any other integer

natural number whose proper divisors sum to one less than itself

mathematical recursive sequence

number whose divisors add to a multiple of that number

numbers with a perfect number of factors and a perfect sum of factors

natural number sharing its abundancy index with at least one other number

positive integer which equals half of the sum of the divisors of the sum of its divisors

positive integer whose divisors have a harmonic mean that is an integer

sum of all proper divisors of a natural number

pairs of positive integers such that the sum of the proper divisors of either number is one more than the other number

a type of integer with many divisors

concept in mathematics

the smallest number whose sum of divisors exceeds some given bound

natural number n for which the equality n=1+k(σ(n)−n−1) holds for some k

abundant number whose proper divisors are all deficient numbers

odd number which would have been a perfect number if one of its composite factors were prime