Base 13 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 87: | \[{13^{87}-1\over12}\] | 3 × 61 × 1973 × 2843 × 3539 × 8527 × 846041103974872866961<21> × 808648601294417626878199<24> × 32188981953012087857559765746138617<35> |