Congruence $320 \equiv 1 (\text{mod }x)$ I have the following congruence $320 \equiv 1 (\text{mod }x)$
And the question is : find all the modulos $x$ that make this congruence true.

$320 \equiv 1 (\text{mod }x)  \rightarrow 320-1 \equiv 0 (\text{mod }x) \rightarrow 319 \equiv 0 (\text{mod }x) \rightarrow x=11$ or $29$, since that only works for the divisors.
