How can we prove that there are no other integers with $\phi(n)=2$ besides 3,4,6?
4530
For which natural numbers are $\phi(n)=2$?
149509
What method would you go through to find an $n$ such that $\phi(n)=100$?
138819
Prove that $\phi(n) \geq \sqrt{n}/2$
25023
How do you prove that there are infinitely many primes of the form $5 + 6n$?
120629
Prove if $n$ has a primitive root, then it has exactly $\phi(\phi(n))$ of them
99037
Prove the sum of all numbers that do not have a multiplicative inverse mod $n$
22977
How many $6$-integer subsets of $\{1, 2, 3, \ldots, 20\}$ have no consecutive integers?
158582
Prove that $\{\frac{\phi (n)}{n}\}_{n \in \Bbb N}$ is dense in $[0,1]$
9753
How to solve the equation $\phi(n) = k$?
155926
Prove there are k consecutive non-squarefree integers
49136
How to compute $m$ value from RSA if $phi(n)$ is not relative prime with the $e$?
90806
Find all positive integers $n$ such that $n$ is divisible by all the positive integers less than or equal to $\sqrt{n}$
15000
Show that number of elements in $(Z/nZ)^*$ is $\phi (n)$
109305
Non-existence of natural numbers such that $\sqrt{n} +\sqrt{n+1} <\sqrt{x} +\sqrt{y} <\sqrt{4n+2}$
94558
Show that $\phi(mn) = \phi(m)\phi(n)\frac{d}{\phi(d)}$
153062
Question about irreducible Gaussian integers
46741
Prove that $n$ divides $\phi(a^n -1)$ where $a, n$ are positive integer without using concepts of abstract algebra