TLDR: In octal system, the weight of the digit in a position is an exponent of 8. So 31 = (3×8¹ + 1×8⁰) = (3×8 + 1×1) = 24 + 1 = 25.

Despite all of its privacy concerns, one can’t really get rid of it if everyone around is using it as the default communication mode, unless you’re a social outcast. The thing with communication apps is that they aren’t a personal choice.