1837

1837 = 11 x 167.

1837 is a centered dodecagonal number (or a star number) (A003154).

1837 is a concentric hexagonal number (A032528).

1837 is a value of n for which 2n (3674) and 7n (12859) together use each of the digits 1 to 9 exactly once.

1837, 1838, and 1839 are consecutive semiprimes (A056809).

1837 is the number of intersections of diagonals in the interior of a regular 18-gon (A006561).

Source: What's Special About This Number?

3750

3750 = 2 x 3 x 5 x 5 x 5 x 5 (A143207).

3750 is a concentric hexagonal number (A032528).

3750 is the first of four consecutive squareful numbers (A070284).

3750 is 110000 in base 5 (A033042).

3750 is the sum of two powers of 5 (A055237).

3750 is a number n such that n and the square of n are sums of two successive primes (A213739).

Source: What's Special About This Number