In number theory, euler theorem (also called Fermat-euler theorem or Euler function theorem) is about the property of congruence. Euler theorem is named after Swiss mathematician leonhard euler, and this theorem is considered as one of the most beautiful theorems in mathematics.

Euler theorem showed that if n, a is a positive integer and n, a is coprime, then:

Swiss mathematician leonhard euler (1April 70715 ~1September 783 18) went to university of basel to study at the age of 13, and was carefully guided by the famous mathematician Bernoulli. Euler is a prolific and outstanding mathematician in the history of science. In order to organize his works, the Petersburg Academy of Sciences spent 47 years.