Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 106: | \[{21^{106}-1\over20}\] | 2 × 11 × 107 × 1697 × 8693 × 207612155793974069<18> × 372515213872960388437<21> × 4555268603071594349347155493<28> × 167223466685805761701453712891<30> × 3494212075791575531835909274237181<34> |