(2+1)(2^2+1)(2^4+1).(2^64+1)
=(2-1)(2+1)(2^2+1)(2^4+1).(2^64+1)
=((2^2-1)(2^2+1))(2^4+1).(2^64+1)
=(2^4-1)(2^4+1).(2^64+1)
.
=(2^64-1)(2^64+1)
=2^128-1
2的n次方的个位上是以2,4,8,6循环.
128/4=32
所以,2^128的个位上是6
那么2^128-1的个位上是6-1=5