11 is a typical number. It falls between 10 (the end of the decimal count) and 12 (the end of the ancient division of a circle) and it cannot very well be reproduced with the euclidean tools although it is possible.

Possibly this is the reason that in some languages 11 is called the 'crazy number' and events like carnival are (at least in some countries) initiated at 11th November at 11 hour in the morning: (11-11;11:11)