Here are the largest solutions that were sent in.

Matthew from South Farnham School:

4096, by doing 4 to the power 3 to the power 2, which is (4 x 4 x 4) x (4 x 4 x 4) = 64 x 64 = 4096.

Josh from Alameda School:

1 048 576, which is 32 to the power of 4 (32 x 32 x 32 x 32).

Greenford School, Dorset sent in 8 796 093 022 208, which is 2 to the power of 43.

Charlotte, Agnes, Susannah and Miranda from Headington Junior School offered 109 418 000 000 000 000 000, which is about 3 to the power 42.

In fact the exact value of 3^{42} is 109 418 989 131 512 359 209 can you say it aloud easily?