27226...34291 (42-digits)

This number is a prime.

                              27 2261127249 4527272802 7296162731 9532734291

The smallest prime formed from the concatenation of six consecutive triangular numbers {2722611, 2724945, 2727280, 2729616, 2731953, 2734291} such that the reverse concatenation of the same triangular numbers produces another prime (273429127319532729616272728027249452722611). [Bajpai]