$ sudo apt-get remove gmp-ecm 

Uninstall gmp-ecm including dependent package

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

$ sudo apt-get remove --auto-remove gmp-ecm 

Use Purging gmp-ecm

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

$ sudo apt-get purge gmp-ecm 

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 gmp-ecm 

See Also,