9491

This number is a prime.

Prime 9491 is the smallest prime p with an extremely rare property: the largest prime factor of the concatenated number (p+3)(p+2)(p+1) is p itself: (9494)(9493)(9492) = 949494939492 = 2 x 2 x 3 x 11 x 19 x 113 x 353 x 9491. The only other known prime of this type is 2723957777, with (2723957780)(2723957779)(2723957778) = 272395778027239577792723957778 = 2 x 3 x 101 x 373 x 21283 x 22391 x 928351 x 2723957777. If there is another one it is at least 30 digits long. [Keith]