# 163 and Ramanujan Constant

$e^{\pi \sqrt{163}}$
is almost a whole number !

$\sqrt{-163}$
is the last one of the list d which allows unique prime factorization in Z[d].

$d = \sqrt{-1}, \sqrt{-2}, \sqrt{-3}, \sqrt{-7}, \sqrt{-11}, \sqrt{-19}, \sqrt{-43}, \sqrt{-67}, \sqrt{-163}$

Why $\sqrt{-5}$ not in d?

6 = 2 x 3
$6 = (1 + \sqrt{-5}).(1 - \sqrt{-5})$