109 is a prime number.
109 has a representation as a sum of two squares: 109 = 32 + 102.
107 and 109 form a twin prime pair.
109 is the hypotenuse of a primitive Pythagorean triple: 1092 = 602 + 912.
109 is a centered triangular number.
109 is the smallest number that contains more digits than its square: 1092 = 11881.
109 is the smallest number that is palindromic in bases 5 (414) and 9 (131).
109 is the atomic number of the element meitnerium.Source: Number Gossip
