649

649 = 11 x 59.

649 is a semiprime whose digits are each a semiprime (A107342).

649 is the smallest number n so that n² is 1 more than 13 times a square: 649² = 1 + 13(180)².

649 is 345 in base 14.

649 is a brilliant number (A078972).

Gliese 649 is a red dwarf star in the constellation of Hercules.

Source: What's Special About This Number?