Pierre De Fermat
Most famous for FermatsLastTheorem, but also known for his "little" theorem, which says that
- a^p=a(mod p).
This was generalised by Euler to
- a^phi(n)=1(mod n) for (a,n)=1
which is the basis of the RSA cryptosystem.
Work by Fermat is also said to have inspired IsaacNewton in his invention of calculus.