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Leonhard Euler (1707–1783) was a Swiss mathematician and physicist. He developed important concepts and proved mathematical theorems in fields as diverse as calculus, number theory and topology. Euler introduced much of the modern mathematical terminology and notation, particularly for mathematical analysis, such as the notion of a mathematical function. He is also renowned for his work in mechanics, optics and astronomy. Euler is considered to be the preeminent mathematician of the 18th century and one of the greatest of all time. According to Guinness World Records, he is also the most prolific; his collected works fill 60 to 80 quarto volumes. Euler was featured on the sixth series of the Swiss ten-franc banknote and on numerous Swiss, German and Russian stamps. The asteroid 2002 Euler was named in his honor. This portrait of Euler was created by the Swiss painter Jakob Emanuel Handmann in 1753 and is now in the collection of the Kunstmuseum Basel.Painting credit: Jakob Emanuel Handmann; restored by Bammesk