Finding All Integers in such that $\phi(n)=80$
9753
How to solve the equation $\phi(n) = k$?
102174
Proving that all terms in sequence are positive integers (Recursive)
49938
Proof of $a^{\phi (n) +1} \equiv a \pmod{\! n} $ Carmichael generalization of Fermat-Euler's theorem.
53263
Show $\sum\limits_{d|n}\phi(d) = n$.
33505
Show that every large integer has a large prime-power factor
16722
Proving Gaussian Integers are countable
27069
sum of all positive integers less than $n$ and relatively prime to $n$
148906
Finding integers $m,n$ such that $(m-n)^2=4mn/(m+n-1)$
53042
Find solutions to $\varphi\left(n\right)=2^{32}$
91485
Finding an uncountable chain of subsets the integers
156660
The set of all strictly increasing sequences of natural numbers
117681
For which Natural $n\ge2: \phi(n)=n/2$
157652
Fermat's Last Theorem for Gaussian Integers (excluding the integers or  same pure imaginaries)
142931
Problem on Euler's Phi function
4512
Is there a direct, elementary proof of $n = \sum_{k|n} \phi(k)$?
61858
Is there $\phi(n)=n/6$
32653
Smallest integer divisible by all up to $n$