Just use your calculator. That's what I did.
The next one is 65536 times by itself (Squared)
which equals:
4294967296
and I see I've just completed my entire thread in two posts Doh!
Just as well I put it in stupid zone. Useless fact: It only takes five calculations of square numbers, starting from 2, to get to a number greater than one hundred milliion.
I really should have thought this one through better.
“What deep wounds ever healed without a scar?” -Lord Byron