Since that is a rather large power of two, I suggest that you start with simple examples and see if you can find a pattern:
[itex]2^0= 1[/itex]. Remainder on division by 7: 1
[itex]2^1= 2[/itex]. Remainder on division by 7: 2
[itex]2^2= 4[/itex]. Remainder on division by 7: 4
[itex]2^3= 8[/itex]. Remainder on division by 7: 1
[itex]2^4= 16[/itex]. Remainder on division by 7: 2
[itex]2^5= 32[/itex]. Remainder on division by 7: 4
[itex]2^6= 64[/itex]. Remainder on division by 7: 1
[itex]2^7= 128[/itex]. Remainder on division by 7: 2
[itex]2^8= 256[/itex]. Remainder on division by 7: 4
Get the idea?