Leonard Euler was without any doubt the most outstanding mathematician of the Enlightenment and one of the greatest scientists in the history of this science. Although his name is primarily inextricably linked with mathematical analysis (series, limits and differential calculus), his titanic scientific work was not limited to this. He made fundamental discoveries in geometry and number theory, created a new field of research from scratch - graph theory, and published countless papers on a variety of issues: hydrodynamics, mechanics, astronomy, optics and shipbuilding. Euler also updated and established a system of mathematical notations that are very close to modern ones. He had extensive knowledge in every field of science; his incredible mind left us with a legacy of unsurpassed works written during the years of work in the best academies of the 18th century: St. Petersburg and Berlin.