i don't know how many digits does this have. i didn't calculate. Use logarithms for that.

But i can tell you the last 7 numbers in the decimal expansion.

use euler's generalization of fermat's little theorem to get

this implies why?

the above two give .

let

so

the inverse of 7 wrt 10^7 is 2857143(you can go to wolframalpha for this or can do some long time computing yourself )

so,

hence the last 7 digits of are

i know that 7 is nothing compared to the number of digits in 7^{999999} but still...