3^1=3末位是3
3^2=9末位是9
3^3=27末位是7
3^4=81末位是1
3^5=243末位是3
3^6=729末位是9
.
故3的n次方的末尾数每4个整数以循环
由2013=503×4+1
3^2013的末尾与3^1的末尾数相同为3.