Full steps how to solve

 First figure out the exponent.

2 $$\mathrm{\ }$$ ^256=2115792089237316195423570985008687907853269984665640564039457584007913129639936256

Now multiply 136*2115792089237316195423570985008687907853269984665640564039457584007913129639936256=287747724136275002577605653961181555468044717914527116709366231425076185631031330816