List questions from divisor-sum

Published on 28 Mar 2026 - 6:06

870

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When $p$ is an odd prime, is $(p+2)/p$ an outlaw or an index?

Published on 26 Mar 2026 - 9:17

83

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Does there exist an integer $m$ which is not in the image of $D(n)=2n - \sigma(n)$?

Published on 26 Mar 2026 - 9:17

69

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How to go about getting an answer to this problem?

Published on 12 Jan 2017 - 12:17

246

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On odd perfect numbers $n$ and $\sigma\left(n^\lambda\right)$

Published on 26 Mar 2026 - 9:20

183

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If $N = q^k n^2$ is an odd perfect number with $k > 1$ and $N = \frac{q(q+1)}{2} \cdot d$ for some $d > 1$, then what is $d$?

Published on 26 Mar 2026 - 9:18

247

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Is there a (conjectured) relationship between triangular numbers and friendly numbers?

Published on 26 Mar 2026 - 9:16

161

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A congruence involving odd perfect numbers and the Möbius function

Published on 26 Mar 2026 - 9:49

326

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If we suppose, that a perfect odd number exists, can we determine whether infinite many exist?

Published on 26 Mar 2026 - 12:07

697

Views

How did Descartes come up with the spoof odd perfect number $198585576189$?

Published on 26 Mar 2026 - 10:45

236

Views

Prove that the sum of the divisor function equals to sum of the floors

Published on 28 Mar 2026 - 2:50

90

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Can this heuristic on odd perfect numbers be made rigorous?

Published on 26 Mar 2026 - 12:06

211

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On perfect numbers, Gauss' trick and geometric series

Published on 07 Feb 2017 - 1:19

99

Views

Is $D(x) + D(y) \leq D(xy)$ true when $\gcd(x, y)=1$ and $xy$ is deficient?

Published on 13 Feb 2017 - 18:23

76

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On a simple combination between Thābit ibn Qurra theorem and Wilson-Lagrange

Published on 19 Feb 2017 - 17:58

List Question

Understanding Gauss Theorem:$n=\sum_{d|n}\phi(d)$

When $p$ is an odd prime, is $(p+2)/p$ an outlaw or an index?

Does there exist an integer $m$ which is not in the image of $D(n)=2n - \sigma(n)$?

How to go about getting an answer to this problem?

On odd perfect numbers $n$ and $\sigma\left(n^\lambda\right)$

If $N = q^k n^2$ is an odd perfect number with $k > 1$ and $N = \frac{q(q+1)}{2} \cdot d$ for some $d > 1$, then what is $d$?

Is there a (conjectured) relationship between triangular numbers and friendly numbers?

A congruence involving odd perfect numbers and the Möbius function

If we suppose, that a perfect odd number exists, can we determine whether infinite many exist?

How did Descartes come up with the spoof odd perfect number $198585576189$?

Prove that the sum of the divisor function equals to sum of the floors

Can this heuristic on odd perfect numbers be made rigorous?

On perfect numbers, Gauss' trick and geometric series

Is $D(x) + D(y) \leq D(xy)$ true when $\gcd(x, y)=1$ and $xy$ is deficient?

On a simple combination between Thābit ibn Qurra theorem and Wilson-Lagrange

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