Euler Type Generalization of Wilson's Theorem
  In this short note, we introduce an Euler analogue of Wilson's theorem; $a_1a_2... a_{\phi(n)}\equiv (-1)^{\phi(n)+1}~({\rm mod}~n)$ say, where ${\rm gcd}(a_i,n)=1$. 
Mehdi Hassani, Mahmoud Momeni-Pour