If $n=2\phi(n)$, then $n=2^j$.
880
Find all n such that $\phi(n) = n/2$
119118
Prove $n\mid \phi(2^n-1)$
157711
Number Theory: Prove that $m | \phi(a^m - 1)$
143357
Comparing $2^n$ to $n!$
138819
Prove that $\phi(n) \geq \sqrt{n}/2$
22073
Prove by induction that $n^2<n!$
11867
Prove by induction that $n < 2^n$ for all $n \ge 1$
4970
For $n \geq 2$, show that $n \nmid 2^{n}-1$
4776
Prove that the power set of an $n$-element set contains $2^n$ elements
26233
$[K(\zeta_n):K]=\phi(n)$?
15000
Show that number of elements in $(Z/nZ)^*$ is $\phi (n)$
46065
How do you find all $n$ such that $\phi(n)|n$
9753
How to solve the equation $\phi(n) = k$?
84930
How to justify $\phi(n) \ge \sqrt{n}$
46741
Prove that $n$ divides $\phi(a^n -1)$ where $a, n$ are positive integer without using concepts of abstract algebra
85731
Prove by induction that $n! > n^2$
114136
Euler's $\phi(n)$ function and solutions of $\phi(n) = 4294967296=2^{32}$