Euler's criterion


Euler's criterion

[′ȯi·lərz krī′tir·ē·ən] (mathematics) A criterion for the congruence x n ≡ a (mod m) to have a solution, namely that a φ/d≡1 (mod m), where φ = φ(m) is Euler's phi function evaluated at m, and d is the greatest common divisor of φ and n.