1775 = 5 x 5 x 71.
1775 is 11011101111 in base 2 (binary). It has exactly nine 1s in its binary expansion (A023691).
1775 is a member of the Fibonacci-type sequence beginning with 1 and 7 (A022097).
1775 is the sum of all odd numbers in the range 350 to 359 (A053742).
1775 is the smaller of two consecutive numbers that are not the sum of three nonzero squares (A178615).
Source: What's Special About This Number?