Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 156: | \[{21^{156}-1\over20}\] | 22 × 11 × 132 × 17 × 53 × 61 × 79 × 157 × 421 × 463 × 547 × 1171 × 3181 × 6709 × 11701 × 32969 × 101089 × 189437 × 629773 × 516094151 × 7021471715414521<16> × 23509884574335185209<20> × 7691526674487958994017<22> × 80459337199345300130638393<26> × 193538987428465501811153413<27> × 14394080037015419873205085261549<32> |