Is it possible mathematically to get a third number from two numbers, and then back the first two numbers?

Question

Mathematics

Is it possible mathematically to get a third number from two numbers, and then back the first two numbers?

Answer 1

You can, only under certain conditions.
That is, for example, two composite numbers (for the resulting, third): the maximum prime divisor (in the range of a composite number: divisible) and the remainder of the division by this number.
The main condition: a pre-known rule for the formation of a new number, in which there is one single solution to the equation for any mathematical operations between all the numbers of the equation.

Answer 2

Easily! ABC and XYZ -> ABC,XYZ -> ABC and
XYZ

Answer 3

Just put some of the bits under the first number, and some under the second. For example 16 bits.
Separation will be easy too.

Answer 4

For non-negative integers, there are many beautiful options. For example, x, y <-> (2x+1)*2^y. In general, it is possible for any, but a simple formula is enough, perhaps, only in the case of integers.