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Euro notes are not numbered consecutively.
Unlike euro coins, euro notes do not have a national side indicating which country issued them (which is not necessarily where they were printed). This information is instead encoded within the first character of each note's serial number.
The first character of the serial number is a letter which uniquely identifies the country that issues the note. The remaining 13 characters are numbers which, when added up and the digits of the resulting sum then added together again until a single digit remains, give a checksum also particular to that country. Because of the arithmetic of the check-sum, consecutively-issued banknotes are not numbered sequentially, but rather, "consecutive" banknotes are 9 digits apart.
and to make it even more interesting the checksum is calculated like this
Each note has a unique serial number. The serial number contains a check digit (last digit) between 1 and 9, that fulfills the following criterion: if the initial letter is replaced by its position in the alphabet (that is L is 12, M is 13,..., Z is 26), the remainder from division of the resulting number by 9 is 8. The remainder from division by 9 can easily be found by repeatedly adding up parts of the number.
For example: Z10708476264 gives 2610708476264. The remainder from division by 9 can be found by: 26 + 1 + 0 + 7 + 0 + 8 + 4 + 7 + 6 + 2 + 6 + 4 = 71 , 7 + 1 = 8
By replacing the initial letter by a different system, you will get different required remainders. For instance, when replacing the letter by its ASCII value, the remainder will be 0, meaning the resulting number will be divisible by 9 (see Divisibility rule; in this case, the repeated addition will result in 9).
Another example: Z10708476264: the ASCII code for Z is 90, so the resulting number is 9010708476264. The addition of all digits gives 54; 5+4 = 9 - so the number is divisible by 9, or 9010708476264 modulo 9 is 0. |