Leonhard Euler was one of the greatest mathematicians in history, and he also studied and researched nearly every other type of science also. But not only did he produce amazing mathematics that the world had never seen, but he also published at an outrageous rate. He published more than any other single mathematician before him. If the quality of output multiplied by the quantity of output is the formula for greatness, well then Euler may have been the greatest mathematician to ever live.
You see he was studying so many different areas of maths and topics, and as a result, made so many discoveries and innovations that he is nearly always the earliest written reference on a given matter. It was so much so that historians decided, to avoid naming everything after Euler, that some theorems were attributed to the first person who wrote and proved them after Euler.
Imagine that, having a legacy so big that people decided it was only fair to take a couple of discoveries away and hand them to the second place mathematicians! Leonhard Euler was born in Basel, Switzerland and grew up in Riehen. From a very early age, he should phenomenal memory, performing extremely difficult calculations in his head and reciting long poems by heart without much difficulty.
He attended the University of Basel and graduated as a Master of Philosophy where he intensively studied two mathematical geniuses: Isaac Newton and Rene Descartes. He ended up authoring over 800 papers, and all of his work added up does take up a rather impressive fraction of all the mathematical and scientific research made in the 1700s.
This is why you can find so many entities in maths called Euler’s function, Euler’s equation or Euler’s formula. Though many of his formulas have their unique names, so it is hard to know the number of innovations he brought to the field.