1. Digits of the checked sequentially numbered from right to left.
|2. Digits, which turned out to odd places remain unchanged.|
3. The digits that standing on even places, multiplied by 2.
|4. If the result of this multiplication occurs a number greater than 9, it is replaced by the sum of the digits of the result of multiplying - single digit.|
|5. All calculated digits are summarized. If the sum is a multiple of 10, the account number is possibly valid.|