Base36
https://en.wikipedia.org/wiki/Base36
https://www.wdic.org/w/SCI/36%e9%80%b2%e6%b3%95
ruby
$ irb irb(main):001:0> 40.to_s(36) => "14" irb(main):002:0> 1248.to_s(36) => "yo" irb(main):003:0> 918237918.to_s(36) => "f6p0wu"
irb(main):007:0> 40.to_s(2) => "101000" irb(main):008:0> 40.to_s(16) => "28" irb(main):009:0> 40.to_s(36) => "14" irb(main):010:0> 40.to_s(37) ArgumentError: invalid radix 37 from (irb):10:in `to_s' from (irb):10 from /usr/bin/irb:12:in `' irb(main):011:0>
