163 is the natural number following one hundred sixty-two and preceding one hundred sixty-four.
Given 163, the Mertens function returns 0. Multiplied by -1, it is a Heegner number.
163 figures in an approximation of π, in which 
. Also, it appears in the Ramanujan constant , in which 
almost equals the integer 262537412640768744. Martin Gardner famously asserted that this identity was exact in a 1975 April Fools' hoax in Scientific American; in fact the value is 262537412640768743.99999999999925007259...
163 is a strictly non-palindromic number, it is not palindromic in any base from base 2 to base 161.
One hundred sixty-three is also: