No, but you can make any user an Administrator, just log on as Admin, select the user you want to be an administrator, edit their profile and change the user type to administrator
Sure, it's not impossible, but we don't recommend you to do it. If we wanted to allow users to change the admin username, we would have made it easier, by letting users do it in the forums, instead of modifying the database. But we don't recommend you changing the name. Just do what HuwR says instead.