690

690 = 2 x 3 x 5 x 23.

690 is the smallest number that can be written as the sum of a triangular number, a cube, and a Fibonacci number.

690 is the sum of six consecutive primes: 690 = 103 + 107 + 109 + 113 + 127 + 131.

690 has the representation 690 = 3⁶ - 39.

690 is a divisor of 91² - 1.

Source: What's Special About This Number?