Beware of the decimal point! It will kill your high precision.
If you enter
N[E^2,20]
you get 7.3890560989306502272.
But if you enter
N[E^2. ,20]
You get only 7.38906.
If you need to use fractional amounts rationalize them fiirst
If you want a high precision estimate for 2^2.125.
enter
N[2^Rationalize[2.125, 0], 20]
instead of
N[2^2.125, 20]
.The 0 in Rationalize[] makes sure the decimal is rationalized completely, not just substituted by an approximation.
