There ain't no fifthtillion.
There is a pentillion.
Million = ten to the 6ixth power 1 000 000
Billion = ten to the 9th power 1 000 000 000
Trillion = ten to the 12th power 1 000 000 000
Quadrillion = ten to the 15th power 1 000 000 000 000
Pentillion = ten to the 18th power 1 000 000 000 000 000
Sextillion = ten to the 21st power 1 000 000 000 000 000 000
the "sex" refers to the six groups of zeros. It goes up like sept, oct, non dec... getit?
JCF
Try Wikipedia. you'll learn more.