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Theorem

Euler's Criterion

Number Theory

Euler's Criterion is a formula for determining whether an integer is a quadratic residue modulo an odd prime: for a prime p and an integer a coprime to p, a raised to the power of half of p minus one is congruent to one modulo p exactly when some integer squared is congruent to a modulo p, and congruent to negative one modulo p otherwise. The criterion can be restated concisely using the Legendre symbol, and it dates from a 1748 paper by Leonhard Euler.

Facts
Statement
A formula for determining whether an integer is a quadratic residue modulo a prime. 1
Proof Year
1748 1
Classification
Statement Form
Identity or Equation 1
Connections

Has Statement Form

Equation, Concepts

Entity-backed identity for the statement-form enum value this theorem already carries, resolved to a mathematics concept by an explicit value-to-entity map (phase 3 bucket conversion, docs\design_entity_backed_browse_buckets_20260928.md). The statement-form fact itself stays on the theorem unchanged.

Identity, Concepts

Entity-backed identity for the statement-form enum value this theorem already carries, resolved to a mathematics concept by an explicit value-to-entity map (phase 3 bucket conversion, docs\design_entity_backed_browse_buckets_20260928.md). The statement-form fact itself stays on the theorem unchanged.

In Branch

Source Euler's criterion (Wikipedia)

Named After

Leonhard Euler, Mathematicians

Derived from the theorem's own name (unambiguous possessive-token match to exactly one live mathematician entity, w-bfill-g5-0924 browse backfill)

Proved By

Sources
1. Euler's criterion (Wikipedia)
  • Intro, sentence 1
    Euler's criterion is a formula for determining whether an integer is a quadratic residue modulo a prime
  • Intro, sentence after the Legendre symbol reformulation
    The criterion dates from a 1748 paper by Leonhard Euler.
  • In Branch: Number Theory, Lead sentence
    In number theory, Euler's criterion is a formula for determining whether an integer is a quadratic residue modulo a prime.
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