The number, e, is special. In the same way that pi is special for circles, e is special for many reasons.
Its unique value is makes its exponential function give the value of its own slope and its own area under the curve.
No other constant value, C , will do that.
Try it ...

The demonstration only gives a rough approximation of the value of e. What is the value really?
Why is this function, (e)^x , so useful?