/usr/lib/x86_64-linux-gnu/libarpack++.so.2 is in libarpack++2c2a 2.3-6.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libarpack++.so.2.0.0
/usr/lib/x86_64-linux-gnu/libarpack++.so.2.0.0