My free tip of the day: Have you realised the bus numbers in Helsinki are based on the postal codes their routes end in? Makes guessing their route and destination a bit easier (for locals).
The numbers have also offered us much more entertainment I could ever have imagined before kids: first recognising numbers, then learning that all with two digits are tens, and the three digit ones, the hundreds, go far (the neighbour cities Espoo or Vantaa). Also, we can use them for simple math problems: if the bus number is 52, how much is 5+2? What about 5-2?