/usr/lib/x86_64-linux-gnu/libatlas.so.3 is in libatlas3-base 3.10.3-5.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libatlas.so.3.10.3
/usr/lib/x86_64-linux-gnu/libatlas.so.3.10.3