In the April 1975 issue of Scientific American, Martin Gardner wrote (jokingly) that Ramanujan's constant (e^(*sqrt(163))) is an integer. The name "Ramanujan's constant" was actually coined by Simon Plouffe and derives from the above April Fool's joke played by Gardner. The French mathematician Charles Hermite (1822-1901) observed this property of 163 long before Ramanujan's work on these so-called "almost integers." [Aitken]

The smallest prime p whose pth power pp contains a pandigital substring: 163163 = 38599...(5941863207)...95547. Note that (163) is a semiprime with larger prime factor 19 which is the smallest prime q whose qth power
qq is pandigital, and that the concatenations 16319 and 19163 are also primes. [Beedassy]

163 is the least number k such that decimal representation of 1/k has
period of length 81. It is one of a few exceptions to the rule that
k=3^(n+2) is the least number with 1/k having period 3^n. [Noe]

The smallest 3-digit prime whose absolute value of the differences between any two of its digits are also prime. [Green]

The largest squarefree integer n such that the ring of integers of the field Q(sqrt(-n)) has unique factorization. [Luen]

The prime number 163 contains only the three positive
triangular digits, as does the 163rd triangular number
(13366). [Gaydos]

(There are 10 curios for this number that have not yet been approved by an editor.)