List questions from divisor-sum

Published on 26 Mar 2026 - 16:56

555

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What is known about multi-perfect numbers?

Published on 26 Mar 2026 - 16:57

2.2k

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When is the sum of divisors a perfect square?

Published on 19 May 2015 - 17:07

470

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Estimate of sum of divisors up to a certain number?

Published on 21 May 2015 - 5:44

67

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Is there a solution to this system of equations?

Published on 22 May 2015 - 3:20

112

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What is $\gcd(\sigma(q^{k-1}), \sigma(q^k))$?

Published on 23 May 2015 - 15:48

41

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A question about $\gcd$ and divisibility

Published on 23 May 2015 - 16:23

83

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Is it possible to compute $\sigma(AB)$ if $\gcd(A, B) = C > 1$?

Published on 25 May 2015 - 18:13

220

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If $q^k n^2$ is an odd perfect number with Euler factor $q^k$, can $q = 73$ hold?

Published on 26 Mar 2026 - 18:40

580

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Proof that odd perfect numbers cannot consist of single unique factors?

Published on 26 Mar 2026 - 18:41

380

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For every odd $n\in\mathbb{N}$, is it true that $\sigma(n) < 2n$?

Published on 26 Mar 2026 - 18:41

257

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Prove that there exist $2015$ consecutive abundant numbers

Published on 26 Mar 2026 - 18:30

99

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Is $p(n) = 2^{n²+n-1} - n² - n + 1$ abundant for all $n >1$?

Published on 26 Mar 2026 - 18:40

132

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Probable Candidates for the numbers whose sum of divisors is prime?

Published on 09 Jun 2015 - 15:23

7.8k

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Find the sum of reciprocals of divisors given the sum of divisors

Published on 18 Jun 2015 - 15:14

List Question

Number $N>6$, such that $N-1$ and $N+1$ are primes and $N$ divides the sum of its divisors

What is known about multi-perfect numbers?

When is the sum of divisors a perfect square?

Estimate of sum of divisors up to a certain number?

Is there a solution to this system of equations?

What is $\gcd(\sigma(q^{k-1}), \sigma(q^k))$?

A question about $\gcd$ and divisibility

Is it possible to compute $\sigma(AB)$ if $\gcd(A, B) = C > 1$?

If $q^k n^2$ is an odd perfect number with Euler factor $q^k$, can $q = 73$ hold?

Proof that odd perfect numbers cannot consist of single unique factors?

For every odd $n\in\mathbb{N}$, is it true that $\sigma(n) < 2n$?

Prove that there exist $2015$ consecutive abundant numbers

Is $p(n) = 2^{n²+n-1} - n² - n + 1$ abundant for all $n >1$?

Probable Candidates for the numbers whose sum of divisors is prime?

Find the sum of reciprocals of divisors given the sum of divisors

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