510

This number is a composite.

The concatenation of 510 with itself (510510) is the product of the first 7 primes and also the product of the 7^th through 10^th Fibonacci numbers (13, 21, 34, and 55). [Zerger]

(Continuing the previous curio) The difference between the next prime (19) and the next Fibonacci number (89 - also a prime) is 70, which is the product of the Fibonacci subscripts above. [Trotter]