Is combining two random numbers to create a larger random number considered good practice?

Is combining two random numbers to create a larger random number
considered good practice?

Suppose I have a function that can generate random numbers of different
lengths. So I can generate a number of 32-length and of 512-length also.
But I want to know what would be the security impact if I combine 16
32-length strings to create a 512-length string. Will the security be
equal to generating the 512-length string directly form the algorithm or
concatenating is same ?