You can configure NumLock to work with Mac OS X version 10.9 (Mavericks), by following these steps:
- Launch the System Preferences application
- Click Security & Privacy
- Select Privacy tab
- Choose the Accessibility row
- Click the lock to make changes, and enter your administrator's name and password.
- Drag the NumLock app icon (probably in your Applications folder) to the window under "Allow the apps below to control your computer."
Thanks to user Alantaylor1 for the guidance.