List questions from divisor-sum

Published on 26 Mar 2026 - 22:19

132

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On a criterion for almost perfect numbers using the abundancy index

Published on 28 Mar 2026 - 18:11

219

Views

On the Density of Deficient Odd Numbers and Abundant Integers

Published on 26 Mar 2026 - 22:15

76

Views

Does "sum of divisors" function attain every value of the form $kn$?

Published on 09 Apr 2016 - 15:07

182

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How to generate the sequence of prime building blocks of the colossally abundant numbers: $2, 3, 2, 5, 2, 3, 7, 2, 11, 13, 2, 3, 5, 17, 19, 23, 2,...$

Published on 14 Apr 2016 - 14:16

1.1k

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Proof that $\sum_{d|m} |\mu(d)|=2^n$, where $n$ is the number of distinct prime divisors of $m$?

Published on 27 Mar 2026 - 1:00

4.5k

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How many numbers less than 100 have the sum of factors as odd?

Published on 19 Apr 2016 - 23:23

140

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Are primes less than the sum of divisors?

Published on 21 Apr 2016 - 6:51

831

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Why can this cosine sum function show all primes less than $N^2$?

Published on 27 Mar 2026 - 3:49

37

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If $\sigma(N)$ is odd, $N = 2y^2$, and $y$ is not a power of two, does it follow that $\gcd(2,y) = 1$?

Published on 26 Mar 2026 - 11:01

59

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Question about the validity of a proof involving the abundancy index

Published on 29 Apr 2016 - 21:33

42

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On the relationship between $\max(p_i)$ and $\omega(b)$, if $\sigma(b^2)/b^2$ is bounded above by a specific number $U$

Published on 29 Mar 2026 - 3:35

88

Views

How do I make this formula for the primes more concise?

Published on 20 May 2016 - 21:05

774

Views

What are the applications of Sigma Function?

Published on 21 May 2016 - 2:22

961

Views

Find all the natural numbers $n$ such that $\sigma(n)=15$

Published on 30 May 2016 - 13:53

List Question

A cubic relationship for perfect numbers

On a criterion for almost perfect numbers using the abundancy index

On the Density of Deficient Odd Numbers and Abundant Integers

Does "sum of divisors" function attain every value of the form $kn$?

How to generate the sequence of prime building blocks of the colossally abundant numbers: $2, 3, 2, 5, 2, 3, 7, 2, 11, 13, 2, 3, 5, 17, 19, 23, 2,...$

Proof that $\sum_{d|m} |\mu(d)|=2^n$, where $n$ is the number of distinct prime divisors of $m$?

How many numbers less than 100 have the sum of factors as odd?

Are primes less than the sum of divisors?

Why can this cosine sum function show all primes less than $N^2$?

If $\sigma(N)$ is odd, $N = 2y^2$, and $y$ is not a power of two, does it follow that $\gcd(2,y) = 1$?

Question about the validity of a proof involving the abundancy index

On the relationship between $\max(p_i)$ and $\omega(b)$, if $\sigma(b^2)/b^2$ is bounded above by a specific number $U$

How do I make this formula for the primes more concise?

What are the applications of Sigma Function?

Find all the natural numbers $n$ such that $\sigma(n)=15$

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