Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
61: | \[{21^{61}-1\over20}\] | 15373 × 12519763 × 1128331159687<13> × 1814065850324073713<19> × 57398774322642953389748085156004642469<38> |