The German mathematician Johann Carl Friedrich Gauss (5 letters) is considered to be one of the greatest mathematicians of all time. He made significant contributions to many fields, including number theory, algebra, statistics, analysis, differential geometry, geodesy, geophysics, mechanics, electrostatics, astronomy, and optics. Bernhard Riemann (7 letters) was another famous German mathematician who made significant contributions to analysis, number theory, and differential geometry. Hermann Weyl (4 letters) was a German mathematician who made important contributions to mathematical physics, group theory, and topology.