1311

This number is a composite.

The concatenation of the first and second primes multiplied by the concatenation of the third and fourth primes equals the concatenation of the fifth and sixth primes in reverse order: 23 * 57 = 1311. [Homewood]

The smallest 4-digit number n such that 2^n+n is prime. [Loungrides]

Interestingly, 1311 can be represented as 1311 = 23*57. Note the presence of the first six primes, i.e., 2, 3, 5, 7, 11, and 13. [Gupta]