Euler's criterion

Meaning

Proper Noun

• A theorem which states that, given a positive integer a which is coprime to an odd prime number p, a is a quadratic residue of p if and only if $a^\{(p-1)/2\}$ is congruent to 1 modulo p.

Origin

• Named after Leonhard Euler (1707–1783), Swiss mathematician and physicist, who devised the criterion in 1748.