Base 21 Repunits
Table
Format: small prime × proven prime<size> × (probable prime)<size> × [composite]<size> × {unknown}<size>
127: | \[{21^{127}-1\over20}\] | 509 × 85853 × 123564234215209<15> × 526073566316093<15> × 21045416332383383<17> × 6619201108364006378440292620708869500505245589624095987<55> × 105546738449008968050440888723415799976700232611051102641043<60> |