1803 = 3 x 601.
1803 is a semiprime that becomes a triangular number when its digits are reversed (3081) (A115741).
1803 divides 256 - 1. It also divides 250 - 1 (A003554).
1803 is 2423 in base 9.
1803 is not a number that is the sum of a triangular number, a cube, and a positive Fibonacci number (A115177).
1803 is a non-leap year beginning and ending on a Saturday (A224994).
Source: On-Line Encyclopedia of Integer Sequences