103

103 is a prime number.

103 is the smallest three-digit prime with distinct digits.

101 and 103 form a twin prime pair.

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

103 is the total number of prime numbers that can be displayed on a 12-hour digital clock.

The play Proof, by David Auburn, revolves around a mysterious proof involving prime numbers, left behind in 103 notebooks by a young woman's brilliant father.

Source: Prime Curios!