81180...21111 (235-digits)

This number is a probable-prime (likely to be a prime but we have not (re-)proven it on this site).

                                                 81180 1791781771 7617517417
3172171170 1691681671 6616516416 3162161160 1591581571 5615515415 3152151150
1491481471 4614514414 3142141140 1391381371 3613513413 3132131130 1291281271
2612512412 3122121120 1191181171 1611511411 3112111110 1918171615 1413121111

The smallest prime formed by concatenating in reverse order the first n numbers that end with 1, (n=82), i.e., 811, 801, 791, ..., 101, 91, 81,…, 31, 21, 11, 1. [Loungrides]