Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 104: | \[{21^{104}-1\over20}\] | 23 × 11 × 132 × 17 × 53 × 79 × 32969 × 97241 × 101089 × 189437 × 516094151 × 7021471715414521<16> × 23509884574335185209<20> × 2927682077813715874149933185385605053168690918973651083914101281<64> |