1813

1813 = 7 x 7 x 37.

1813 is the sum of the first 35 semiprimes (A062198).

1813 is the number of trees on 15 vertices with diameter 8.

1813 is 12221 in base 6.

1813 has a representation as a sum of two squares: 1813 = 7² + 42².

1813 divides 48⁶ - 1.

Source: What's Special About This Number?