EAN-13

EAN-13 numbers (commonly used barcodes) are 13 digit numbers which are protected by a special numerical check.
Each digit is multiplied by the alternating factors 1 and 3. The calculation results are then summed together. Finally, to be a valid EAN-13 number, the sum must be divisible by 10.

Example (EAN-13 number: 9780964092303):

9 7 8 0 9 6 4 0 9 2 3 0 3
* * * * * * * * * * * * *
1 3 1 3 1 3 1 3 1 3 1 3 1
= = = = = = = = = = = = =
9 + 21 + 8 + 0 + 9 + 18 + 4 + 0 + 9 + 6 + 3 + 0 + 3 = 90 = N*10


1996-08-21