112

112 is the principal emergency telephone number that can be dialed free of charge from any telephone or any mobile phone in order to reach emergency services (ambulances, fire-fighters and the police) in the European Union (EU)

This choice of number has the following advantages:
1, Using at least two different digits significantly reduces the risk of accidental calls from numeric keypads.
2. In the days of rotary dial telephones, using only those digits that require the least motion of a rotary dial (1 and 2) permitted a dial lock[4] in hole 3 to effectively disable unauthorized access to the telephone network without preventing access to the emergency number 112. The same choice also maximized dialing speed.

Hint: that's a two euro coin...

Hint Hint: 5*20 + 1*10 +1*2