1825

1825 = 5 x 5 x 73.

1825 is an octagonal number (A000567).

1825 is the smallest number whose square begins with three 3s (A131573 and A025286 and A025304 and A034982).

1825 has three representations as a sum of two squares (A025313): 1825 = 12² + 41² = 15² + 40² = 23² + 36².

1825 is the hypotenuse of two primitive Pythagorean triples: 1825² = 767² + 1656² = 984² + 1537².

1825 divides 74² - 1.

Source: What's Special About This Number?