Africa dwarfs Niger: about 30,370,000 km² km² against 1,185,111 km² km². At true size Africa is about 25.6× larger — the whole of Niger fits into Africa roughly 25 times.
The old Mercator map treated both about equally (1× vs 1.1× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
Niger fits 25× into Africa.