Wilson's theorem

E530311

Wilson's theorem is a result in number theory stating that a positive integer n > 1 is prime if and only if the factorial of (n − 1) is congruent to −1 modulo n.

All labels observed (2)

Label Occurrences
Wilson's theorem canonical 1
Wilson’s theorem 1

How this entity was disambiguated

Statements (43)

Predicate Object
instanceOf theorem in number theory ⓘ
appearsIn elementary number theory textbooks ⓘ
appliesTo positive integers n > 1 ⓘ
assumes n is an integer greater than 1 ⓘ
canBeProvedUsing pairing of inverses modulo p ⓘ
properties of multiplicative group modulo p ⓘ
category results about primes ⓘ
results in modular arithmetic ⓘ
characterizes prime numbers ⓘ
equivalenceType if and only if condition ⓘ
equivalentFormulation In (Z/pZ)*, the product of all elements equals −1. ⓘ
The product of all nonzero residues modulo a prime p is congruent to −1 modulo p. ⓘ
example For n = 4, (4 − 1)! = 6 ≡ 2 (mod 4), so 4 is not prime. ⓘ
For n = 6, (6 − 1)! = 120 ≡ 0 (mod 6), so 6 is not prime. ⓘ
For p = 5, (5 − 1)! = 24 ≡ −1 (mod 5). ⓘ
For p = 7, (7 − 1)! = 720 ≡ −1 (mod 7). ⓘ
failsFor composite numbers n > 4 ⓘ
field number theory ⓘ
generalization Wilson primes ⓘ
givesConditionFor n to be prime ⓘ
hasConsequence If (n − 1)! is not congruent to −1 modulo n, then n is composite. ⓘ
If p is prime, then (p − 1)! + 1 is a multiple of p. ⓘ
historicalAttribution first published proof by Joseph-Louis Lagrange ⓘ
known to Ibn al-Haytham (Alhazen) before Wilson ⓘ
holdsFor every prime number p ⓘ
implies If (n − 1)! ≡ −1 (mod n), then n is prime. ⓘ
If n is prime, then (n − 1)! + 1 is divisible by n. ⓘ
involvesOperation multiplication of all nonzero residues modulo n ⓘ
isCriterionFor primality ⓘ
isNot efficient primality test for large n ⓘ
namedAfter John Wilson ⓘ
relatedTo Fermat's little theorem ⓘ
group of units modulo p ⓘ
primality test ⓘ
statement A positive integer n > 1 is prime if and only if (n − 1)! ≡ −1 (mod n). ⓘ
For a prime p, (p − 1)! ≡ −1 (mod p). ⓘ
If n is composite and n > 4, then (n − 1)! ≡ 0 (mod n). ⓘ
usedAs example of a necessary and sufficient condition in number theory ⓘ
usedIn theoretical characterization of primes ⓘ
usesConcept congruence modulo n ⓘ
factorial ⓘ
modular arithmetic ⓘ
yearProved 1771 ⓘ

How these facts were elicited

Referenced by (2)

Full triples — surface form annotated when it differs from this entity's canonical label.

Fermat's little theorem → relatedTo → Wilson's theorem ⓘ
Euler’s theorem → contrastsWith → Wilson’s theorem ⓘ
linked to: Wilson's theorem