Sometimes even when you have the numlock on at boot setting enabled in the BIOS setup, it will be turned off when the login screen occurs with Antergos. This is a way to solve it.
- Install numlockx
pacman -S numlockx
- Edit /etc/lightdm/lightdm.conf
sudo nano /etc/lightdm/lightdm.conf
Now numlock will be enabled at login screen next boot.