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e is the base that is first introduced to our students under natural logarithm but a common misconception because when we teach it with the concept of exponential, e does not derive its letter from the word exponential. e is called e because it's Euler's Number in honor of one of the greatest number theorist and possibly mathematician Leonhard Euler. Interesting too is that Euler didn't come up with logarithms but it was accredited to John Napier. Euler just worked on a mathematics problem I believed that was unsolved and found that it led to this constant e. Something along the lines of, what does 1/0! + 1/1! + 1/2! + 1/3! + 1/4! converge to as well as proving that e is an irrational number?
Btw, just in case you are still thinking, the answer is 7427466391.