Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
| * 247: | \[{21^{247}-1\over20}\] | 79 × 189437 × 583909 × 15109979 × 516094151 × 12061389013<11> × 54921106624003<14> × 22740591300054418772021<23> × 26814043683552997774267<23> × [703728707732012673448487774195255741909082459336018072171332849736417159065602431714861379700717232334545715352774619436261797399955796310766634529361507410156541449497628784210478242168310096438862189506261081558150194177844593<228>] |