"E is the base of natural logarithm." "Natural logarithm is a logarithmic function with base E, and E is an irrational number, which is about 2.7 1828 1828. The symbol e represents a natural constant in mathematics, and the value represented by π is an irrational number. The formula of E-like is E = 1+. )+ 1/(2! )+ 1/(3! )+ 1/(4! )+...+ 1/ ...