trying to disable touchpad in ~/.profile

[Adam Funk]

I'm running a current Ubuntu-MATE system.  This command

xinput --set-prop 13 'Device Enabled' 0

works from the terminal to disable the touchpad, but it doesn't do
anything when I put it in ~/.profile, which I expected to be run while
logging in.  Where do I need to put that command for that to happen?

Thanks,
Adam