/usr/lib/libIrrlicht.so.1.7a is in libirrlicht1.7a 1.7.2+dfsg1-1.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/libIrrlicht.so.1.7a.2
/usr/lib/libIrrlicht.so.1.7a.2