**263** is a prime number.

**263 **is the largest known prime whose square is

strobogrammatic; that is, it is the same number when rotated 180 degrees:

**263**^{2} = 69169.

**263 **is the smallest prime number that is the sum of primes beginning and ending with the digit 1: **263 **= 11 + 101 + 151. Note that the digit sum of each prime is prime and that the digit sum of **263 **is a prime and begins and ends with the digit 1.

**263 **is the only prime with three distinct digits, where one is the product of the other two.

**263 **is the smallest prime formed be inserting a semiprime, 6, between the semiprime's factors, 2 and 3.

**263 **is a number that cannot be written as a sum of three squares.

Anne Frank (and her family) hid from the Nazis in an annex behind the house at 263 Prinsengracht

**263 **in Amsterdam.