Prove for any given positive integer $N$ there exist only finitely many integers n with $φ(n)=N$
71108
Is there an integer $N>0$ such that $\varphi(n) = N$ has infinitely many solutions?
16722
Proving Gaussian Integers are countable
157711
Number Theory: Prove that $m | \phi(a^m - 1)$
96903
How to show via inductive proof (and without the use of the binomial theorem) that $ {n\choose k} \in \mathbb{N} $?
33144
Criterion for $\phi(mn)=m\phi(n)$ to be true
122828
Proof that TREE(n) where n >= 3 is finite?
46065
How do you find all $n$ such that $\phi(n)|n$
129163
Showing that every positive integer can be represented in this form
121723
$\phi(n)=\frac{n}{2}$ if and only if $n=2^k$ for some positive integer k
24446
Prove that for each $n$, there exist $n$ consecutive integers, each of which is divisible by a perfect square larger than $1$.
34960
Lower bound for $\phi(n)$: Is $n/5  1$?
1409
Proving that the given set has at most $2^{n-1}$ elements
106401
Prove: $p-mq | f(m)$ where $m$ is any integer
120629
Prove if $n$ has a primitive root, then it has exactly $\phi(\phi(n))$ of them
20713
The sum of an uncountable number of positive numbers
73454
Prove that $f$ has finite number of roots
50019
Prove $0$ is a partial limit of $a_n$