 Solution

Allocate a fresh array and copy every digit:

function CopyNum(n: number): number
    new(result, len(n))
    for i := 0 to len(n)-1 do
        result[i] := n[i]
    return result

Every coefficient in the digit-array integer representation is unchanged, so the value is unchanged. The new array shares no storage with n; assigning one pointer to the other would instead create reference aliasing. Since the entries are integers, copying the entries also gives the required deep copy of this representation.