This is approx. equal to 2.5699*1099
Generally we use scientific notation for numbers of this magnitute.
You do not need a high powered calculator. Yo can do it yourself. :)
let y=256^(1024^3)
1024^3 = 1073741824
\(y=256^{1073741824}\\ log_{10}y=log_{10}256^{1073741824}\\ log_{10}y=1073741824\;log_{10}256\\ log_{10}y\approx 1073741824\;*\;2.408239965\\ log_{10}y\approx 2585827973\\ 10^{log_{10}y}\approx 10^{2585827973}\\ y\approx 10^{2585827973}\\\)
However, here is the answer using wolfram|alpha :)