(2+1)(2^2+1)(2^4+1)(2^8+1)(2^16+1)(2^32+1)+1
=(2-1)(2+1)(2^2+1)(2^4+1)(2^8+1)(2^16+1)(2^32+1)+1
=(2^2-1)(2^2+1)(2^4+1)(2^8+1)(2^16+1)(2^32+1)+1
=(2^4-1)(2^4+1)(2^8+1)(2^16+1)(2^32+1)+1
=(2^8-1)(2^8+1)(2^16+1)(2^32+1)+1
=(2^16-1)(2^16+1)(2^32+1)+1
=(2^32-1)(2^32+1)+1
=2^64-1+1
=2^64
2^1=2,个位数为2
2^2=4,个位数为4
2^3=8,个位数为8
2^4=16,个位数为6
2^5=32,个位数为2
…………
规律：从2^1开始,个位数字依次为2,4,8,6,每4个循环一次.
64/4=16,正好循环16次.
2^64个位数字为6