List questions from divisibility

Published on 14 Jun 2020 - 15:48

1.6k

Views

Prove that for any positive integer $a,$ $a^{561} \equiv a \pmod{561}.$

Published on 23 Feb 2026 - 3:27

69

Views

Prove that 9 divides $7\cdot5^{2n}+2^{4n+1}$

Published on 16 Jun 2020 - 2:10

76

Views

Find all $a\in\mathbb{N}$ such that $3a+6$ divides $a^2+11$

Published on 16 Jun 2020 - 17:43

891

Views

If a divides $b-1$ and a divides $c-1$ then a divides $bc-1$

Published on 16 Jun 2020 - 18:57

116

Views

$2^r-1$ divides $2^{rs}-1$

Published on 17 Jun 2020 - 7:04

83

Views

Question about divisibility rule by $7$ explanation

Published on 17 Jun 2020 - 7:46

62

Views

How to decide whether $n+\varphi(n)$ can divide $n^2+k$?

Published on 27 Mar 2026 - 20:20

1.2k

Views

Can I get a percent of number without using decimals?

Published on 28 Mar 2026 - 0:35

39

Views

$T$-Annihilators divided by gcd divide another $T$-Annihilator

Published on 29 Mar 2026 - 14:28

566

Views

Triangular numbers divisible by $3$

Published on 01 Apr 2026 - 17:09

127

Views

Proving that $k|(n^k-n)$ for prime $k$

Published on 29 Mar 2026 - 14:29

271

Views

On the equation $\psi(-1+2(\psi(n)-n))=n$ involving the Dedekind psi function, as a characterization of Mersenne primes

Published on 23 Feb 2026 - 3:00

75

Views

Using quadratic residues and/or reciprocity to prove relative primality?

Published on 25 Mar 2026 - 19:04

93

Views

Divisibility Number Theory problem, explanation needed

Published on 01 Apr 2026 - 23:50

List Question

When we are finding a root to a polynomial say f(x), we put some constant

Prove that for any positive integer $a,$ $a^{561} \equiv a \pmod{561}.$

Prove that 9 divides $7\cdot5^{2n}+2^{4n+1}$

Find all $a\in\mathbb{N}$ such that $3a+6$ divides $a^2+11$

If a divides $b-1$ and a divides $c-1$ then a divides $bc-1$

$2^r-1$ divides $2^{rs}-1$

Question about divisibility rule by $7$ explanation

How to decide whether $n+\varphi(n)$ can divide $n^2+k$?

Can I get a percent of number without using decimals?

$T$-Annihilators divided by gcd divide another $T$-Annihilator

Triangular numbers divisible by $3$

Proving that $k|(n^k-n)$ for prime $k$

On the equation $\psi(-1+2(\psi(n)-n))=n$ involving the Dedekind psi function, as a characterization of Mersenne primes

Using quadratic residues and/or reciprocity to prove relative primality?

Divisibility Number Theory problem, explanation needed

Trending Questions

Popular # Hahtags

Popular Questions