24'x18'x21' is 9,072 cubic feet which converts to 67,863.27 US gallons.
About 10 gallons
781.987 gallons.
500 gallons.
92 gallons
You can fit 8 gallons in 8 gallons.
There are 3 gallons
840 half-gallons.
There are 144 gallons in 576 gallons.
There are precisely 107026920 gallons in 107026920 gallons!
7.5 gallons
7.91888967 imperial gallons = 9.51019 US gallons.
9.4 gallons.