This is the smallest repunit (probable) prime with at least 3 1s in base 522.

Currently there are 41 positive bases 2<=b<=1024 without known repunit (probable) primes with at least 3 1s: {185, 269, 281, 380, 384, 385, 394, 396, 452, 465, 485, 511, 574, 598, 601, 629, 631, 632, 636, 640, 649, 670, 691, 693, 711, 713, 752, 759, 771, 795, 861, 866, 881, 932, 938, 948, 951, 956, 963, 1005, 1015}, and these positive bases 2<=b<=1024 have no possible repunit (probable) primes with at least 3 1s because of algebraic factors: {4, 9, 16, 25, 32, 36, 49, 64, 81, 100, 121, 125, 144, 169, 196, 216, 225, 243, 256, 289, 324, 343, 361, 400, 441, 484, 529, 576, 625, 676, 729, 784, 841, 900, 961, 1000, 1024}

To be completed...