By prime factorising the given numbers we get,
243 = 3×3×3×3×3.
So to make it a perfect cube we have to multiply it with 3.
16=4×4.
So to make it a perfect cube we have to multiply it with 4.
500=2×2×5×5×5.
So to make it a perfect cube we have to multiply it with 2.
675=3×3×3×5×5.
So to make it a perfect cube we have to multiply it with 5.