1504 = 25 x 47.
1504 is an example of a number n for which 6n + 1 is a perfect square: 6(1504) + 1 = 9025 = 952.
1504 is the number of anisohedral polyiamonds with 21 cells. A tiling is isohedral if the symmetries of the tiling act transitively on the tiles; a shape is anisohedral if tiles the plane, but not isohedrally.
1504 is a number that is not the sum of a triangular number, a square, and a nonnegative cube. There are 714 such numbers below 2*109.
On Feb. 29, 1504, Christopher Columbus used his knowledge of a lunar eclipse that night to persuade Jamaican tribesmen to provide him and his crew with supplies.