Answer: sextillion

AnswerCrossword Clue
SEXTILLION1,000,000,000,000,000,000,000
SEXTILLIONOne followed by 21 zeros
sextilliona thousand raised to the seventh power (10 to the 21)
sextillionA million raised to the sixth power (1036)
sextillionA thousand raised to the seventh power (1021)