$ sudo apt-get remove lib64gfortran3 

Uninstall lib64gfortran3 including dependent package

If you would like to remove lib64gfortran3 and it's dependent packages which are no longer needed from Ubuntu,

$ sudo apt-get remove --auto-remove lib64gfortran3 

Use Purging lib64gfortran3

If you use with purge options to lib64gfortran3 package all the configuration and dependent packages will be removed.

$ sudo apt-get purge lib64gfortran3 

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 lib64gfortran3 

See Also,