You can reboot it with the <b>reload</b> command, but I don’t think you can power it off remotely.
If you want to stop anyone using it, then shutdown the interfaces, except the one you need to use to access it for command purposes. Or you could shut that one down as well, then you need to repower it to access again, as the command will not be saved (as you lock yourself out with the shutdown command on the interface !).
I think you will still need to switch it off on the box itself if you actually need to power it down. The exercise will do you good anyway