Apply the Luhn algorithm to check identifying numbers

I have a scheduled KNIME flows that processes transactionsdone on mobile devices. I need to be able to validate IMEI numbers to confirm whether they are valid. The check is done with the LUHN algorithm, where every second number is doubled, and then all the separate digits are added together.

There is a further validation step using the formula *(10-(s mod10))* mod10, but this can be done in a math node.

Does anyone have KNIME solution to do this?

tC/.