Wilson's Theorem and quadratic Congruence $x^2 + 1 \equiv 0 \pmod p$
61987
$x^2+1=0$ in $\mathbb{Z}_7$
45171
How prove this $(p-1)!\left(1+\frac{1}{2}+\frac{1}{3}+\cdots+\frac{1}{p-1}\right)\equiv 0\pmod{p^2}$
14809
Existence & uniqueness of solutions of linear congruences $\ cx\equiv b\pmod m$
8784
modulo version of the quadratic formula and Euler's criterion
153647
Elementary number theory and quadratic
33735
The square of an integer is congruent to 0 or 1 mod 4
21874
Solve $x^3+x \equiv 1 \pmod p$
29640
If $x \equiv 1 \pmod 3$ and $x \equiv 0 \pmod 2$, what is $x \pmod 6$?
132587
Prove that the product of coprimes must be congruent to $-1$ or $1 \pmod{m}$
131941
Solve quadratic congruences.
130499
How can $p^{q+1}+q^{p+1}$ be a perfect square?
60305
Proving the congruence $p^{q-1}+q^{p-1} \equiv 1 \pmod{pq}$
95162
For a odd prime $p, \exists a,b$ such that $a^2 + ab + b^2 \equiv 0 \pmod{p} \iff \exists x,y $ such taht $x^2 + xy + y^2 = p$?
11989
$ac\equiv bc \pmod{\!m}\!\!\iff\!\! a\equiv b \pmod{\!\!\frac{m}{(c,m)}}$ [Euclid's Lemma, congruence form]
23153
$\bmod p\!:\ x^2\equiv 1\iff x\equiv \pm1\ $ for prime $p$
74512
How to show $n(n+1)(2n+1) \equiv 0 \pmod 6$?
116686
$p=2^n+1$. Prove that every quadratic nonresidue modulo $p$ is a primitive root modulo $p$