How to know $(\mathbb Z /n\mathbb Z)^*$ is cyclic?
84
For what $n$ is $U_n$ cyclic?
118299
Show that $(\mathbb{Z}[x]/(x^{n+1}))^{\times}\cong \mathbb{Z}/2\mathbb{Z}\times\Pi_{i=1}^n\mathbb{Z}$
125469
What are the generators of $\mathbb{Z}_9^*$?
137422
$\mathrm{card}(\mathbb{Z}^n/M\mathbb{Z}^n) = |\det(M)|$?
75970
$\mathbb Z[1/2]$ is not finitely generated?
73402
Showing that $(\mathbb{Z}/p^{a}\mathbb{Z})^*$ is a cyclic group
5223
$\mathbb{Z}_m \times \mathbb Z_n$ is cyclic if and only if $\gcd(m,n)=1$
102112
Idempotents in $\mathbb Z_n$
69046
Proof of $\mathbb{Q}$ is not cyclic
108775
Identify the ring $\mathbb {Z}[i]/(2 + i) $
48585
Proving that if $G/Z(G)$ is cyclic, then $G$ is abelian
40321
$\operatorname{Aut}(\mathbb Z_n)$ is isomorphic to $U_n$.
4648
Proving that $\mathbb{Z}_m\oplus \mathbb{Z}_n \cong \mathbb{Z}_d\oplus \mathbb{Z}_l $ as groups, where $l=\mathrm{lcm}(m,n)$ and $d=\gcd(m,n)$
28913
How to find a generator of a cyclic group?
93031
How to show that $\mathbb{Z}$ with the operation $m*n=m+(-1)^m n$ is associative?
31933
$x^2 = 1$ in the ring $\mathbb{Z}/n \mathbb{Z}$
123482
How to compute $\mathbb{Z}_n^*$, the unit group of the integers modulo $n$?