# What were the mathematical techniques used for estimating euler number e upto 18 trillion trillion digits ??

While surfing, I came across this mathematical term: $$(1+9^{-4^{6*7}})^{3^{2^{85}}}$$ which approximately equals to the mathematical constant e (Euler's number) upto 18 trillion trillion digits.

What were the mathematical techniques used to approximate e upto 18 trillion trillion digits ?? What were the mathematical techniques used in finding the term $(1+9^{-4^{6*7}})^{3^{2^{85}}}$??

• And uses all the non-zero digits once each in its formulation. Very flashy. Feb 17 '17 at 3:38
• @Joffan Yeah, such numbers are known as Pandigital numbers. You can check more about them if you like. :') Feb 17 '17 at 3:42

$$\lim_{x \to \infty} (1+1/x)^x = e$$
$$\frac{1}{9^{-4^{6*7}}} = 3^{2^{85}}$$