Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| 152: | \[{21^{152}-1\over20}\] | 23 × 11 × 13 × 17 × 229 × 457 × 97241 × 136649 × 609673 × 6629177 × 12061389013<11> × 54921106624003<14> × 8871582886760161<16> × 987749814642143197<18> × 4370570172021545617284038736601<31> × 4510053597010461591911520110711387257<37> × 3794540985952206860593938878074866571399837<43> |