The compositeness test consisting of the application of Fermat's little theorem.
Fermat Compositeness Test
See also
Fermat's Little TheoremExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Fermat Compositeness Test." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/FermatCompositenessTest.html