Euler's criterion
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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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.