11乘101乘10001
=(10+1)*(100+1)*(10000+1)
=(10-1)(10+1)(10^2+1)(10^4+1)/9
=(10^2-1)(10^2+1)(10^4+1)/9
=(10^4-1)(10^4+1)/9
=(10^8-1)/9
=99999999/9
=11111111