Let $n\gt1$, and $h(n)$ denote the number of invertible residue classes $mod n$ that are self-inverses.
40131
If n is such that every element $(\mathbb{Z}/n\mathbb{Z})^{\times}$ is a root of $x^2-1$. Prove that $n$ divides 24.
84
For what $n$ is $U_n$ cyclic?
18108
Show if $(a,p)=1$ there is a unique inverse of $a$ modulo $p$
68635
When is $2$ a quadratic residue mod $p$?
48268
How many $\alpha \in S_n$ are such that $\alpha^2 = 1$?
27942
showing that $n$th cyclotomic polynomial $\Phi_n(x)$ is irreducible over $\mathbb{Q}$
107900
A ring which has many distinct left inverses
110018
Conjugacy classes in $A_n$.
62996
A problem regarding the proof of ${p^nk\choose p^n}\equiv k\mod p$, where $p\nmid k$.
25290
Determine the number of irreducible monic polynomials of degree 3 in $\mathbb F_p[x]$
141909
Prove ${2}^{n}\cdot(2m+1)-1 $ is invertible
119052
Finding invertible elements in $\mathbb{Z}/m\mathbb{Z}$
120968
Isomorphism of stabilizer over $S_n$ to $S_{n-1}$
130162
A complete residue system from an arithmetic progression
48291
Proof that $\mathrm{ker}(f^*) = \mathrm{im}(f)^{\perp} $
133238
Why does $\mathrm{Tor}_0^R(M,N)\cong M\otimes_R N$?
68317
Conjugacy class of $G$ splitting as Conjugacy class of $H\unlhd G$