Leonhard Euler (1707-1783) is widely recognized as one of greatest mathematicians of all time, and the greatest of the 18th century. Other than the quality of his work, one thing that stands out is the sheer *quantity*. I will tell a few interesting facts, because it really is quite astounding. One of the funniest facts: at the time of his death, he had built up such a backlog of mathematical works that after he died, he published 228 papers (source: W. Dunham). He lost his sight in one eye in 1738. And later in his life, his other eye suffered too. By 1771, he was almost entirely blind. What is remarkable is that his productivity seems to not have suffered. In 1775, he produced a paper each week. In that sense, he is the Beethoven of mathematics. Beethoven produced music while deaf, Euler produced mathematics while blind. In total, he produced more than 25 books and treatises and 850 papers. From 1725 to 1783, his publications averaged 800 pages a year. Some have even estimated that Euler alone was responsible for more than a quarter of all mathematics in the 18th century. In 1908, a project was undertaken to combine his collected works, the "Opera Omnia Leonhard Euler". It took more than 100 years to complete, and it was made online in 2022. The result: 81 encyclopedia-sized volumes totaling over 30,000 pages. Finally, as far as I can tell, Euler has more mathematical concepts named after him than any other mathematician ("Euler formula", "Euler line", etc). Gauss is probably the second. If you go to MathWorld and search for "Euler", it gives more hits than even "Gauss".