What is the significance of the mirror numbers? I'd like to hear insights and theory of the mirror numbers and their possible significance in mathematics and geometry. With mirror numbers I mean these four examples: 432 -> 234 123 -> 321 153 -> 351 987 -> 789 Sum of 432 & 234 is 666 and sum of 153 & 351 is 504, which are famous numbers from historical perspective, namely from Pythagoras, Plato, Archimedes and Revelation of John. Supplementing questions arose on a chat with Dan: 1) How to determine if a number x can be represented as n + rev(n)? 2) How to determine possible n & rev(n) for number x?

This is not terrifically profound, but if $y$ is the mirror of $x$ in base $b$, then $x \equiv y \mod b-1$, while $x \equiv \sigma y \mod b+1$ where $\sigma = 1$ if $x$ and $y$ have an odd number of base-$b$ digits and $-1$ if they have an even number of base-$b$ digits.