By prime factorising 7803,
we get, 7803=3×3×3×17×17
=33×172
We know, a perfect cube has multiples of 3 as powers of prime factors.
Here, power of 3 is 3 but power of 17 is 2.
So we need to multiply another 17 to the factorization to make 7803 a perfect cube.
Hence, the smallest number by which 7803 must be multiplied to obtain a perfect cube is 17.