Example image of eyePlorer eyePlorer map for 'Euler's criterion': Integer Mathematics Modular arithmetic Number theory Prime number Quadratic residue Coprime If and only if Legendre symbol Parity (mathematics) Fermat's little theorem Primitive root modulo n Divisor Euler-Jacobi pseudoprime Quadratic reciprocity List of topics named after Leonhard Euler Gauss's lemma (number theory) Jacobi symbol Criterion Quartic reciprocity Lucas–Lehmer primality test