1509

1509 = 3 x 503.

1509 is the number of disconnected 2-regular graphs on 39 vertices (A165652).

1509 is a number n such that 2n + 1, 4n + 1, and 8n + 1 are all primes (A124041).

1509 is a pinwheel number, satisfying the equation 2n² + 6n + 1 for n = 26 (A059993).

1509 is a number n such that 1 + n + n³ + n⁵ + n⁷ + . . . + n³³ + n³⁵ is prime (A124187).

Source: On-Line Encyclopedia of Integer Sequences