Q: Hide 3 digit number into 5 digit number I have 5 digit number in range 1 - 86400
and 3 digit number 0 - 999
I am looking at combine these 2 (with some logic) with rule length of result should not cross 5 digits.
Should be anble to get back 2 numbers when I need
Can anyone help on this algo?

A: Unfortunately, it isn't possible.  The number of combinations of (a 5-digit number in the range $1$-$86400$, a 3-digit number in the range $0$-$999$) is $(86400)(999) = 86313600$.  That means that any correspondence between these combinations and the set of all $\le 5$ digit numbers will map lots of combinations onto the same number (in fact, the average collision rate will be about $863$).  So given a single number, it is impossible to tell which of the $\sim 863$ combinations produced it.
