$ sudo apt-get remove libhd21 

Uninstall libhd21 including dependent package

If you would like to remove libhd21 and it's dependent packages which are no longer needed from Ubuntu,

$ sudo apt-get remove --auto-remove libhd21 

Use Purging libhd21

If you use with purge options to libhd21 package all the configuration and dependent packages will be removed.

$ sudo apt-get purge libhd21 

If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.

$ sudo apt-get purge --auto-remove libhd21 

See Also,