/usr/lib/x86_64-linux-gnu/libprimesieve.so.8 is in libprimesieve8 6.3+ds-2ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libprimesieve.so.8.3.0
/usr/lib/x86_64-linux-gnu/libprimesieve.so.8.3.0