Mammoth Uncensored Word List:
12 words that are 17 letters long beginning with q in the mammoth uncensored word list.

quadragintilliard quadragintillions quadricentennials quadringentillion quarrelsomenesses quatercentenaries quattuordecillion quindecilliardths quingentilliardth quingentillionths quinquadecillions quinquagintillion