163 is prime and the largest of the nine Heegner numbers. The numbers (1, 2, 3, 7, 11, 19, 43, 67, and 163) are the only positive integers for which the imaginary quadratic field ℚ(√−n) has a class number of 1, a fact that fascinated mathematicians before being proven in the 60s. 163 also appears in one of mathematics most surprising near-coincidences: e^(π√163), known as Ramanujan’s constant, misses being a whole number by less than one trillionth, a consequence between number theory and the theory of elliptic curves.