1431535622177

This number is a prime.

                                                              143 1535622177

The smallest prime obtained from the concatenation in some order of the first six semi-primes, each being the product of two successive primes, {6, 15, 35, 77, 143, 221}, i.e., 143=11*13, 15=3*5, 35=5*7, 6=2*3, 221=13*17, 77=7*11. [Loungrides]