Simple but deadly
Number Theory
Level
4
Let \(u=2^{2015}-1\). Evaluate the congruence
\[\varphi\left(u\right) \pmod{2015}\]
where \(\varphi(u)\) is the Euler totient function.
Tip: You probably don't want to compute \(\varphi(u)\) because that would be, well, rather large -- there is a nice way around it.
by
Dylan Pentland