Mammoth Uncensored Word List:
18 words that are 21 letters long beginning with c in the mammoth uncensored word list.

chemolithoheterotroph chemolithotrophically cholecystogastrostomy cholecystojejunostomy cholecystolithotripsy cholecystonephrostomy chronostratigraphists clinicopathologically colpoperineorrhaphies compartmentalisations compartmentalizations constitutionalization contemporaneousnesses countercountermeasure counterdemonstrations counterinterpretation counterproductiveness crystalloluminescence