A valid credit card number has several fields and each of them has a meaning. For the technically inclined, this number complies to the ISO 7812 numbering standard. An contains a six-digit issuer identification number (IIN), an individual account identification number, and a single digit checksum.
The credit card numbers you generate on this page are completely random. When we say they are valid, we merely imply that they are a possible combination of characters which will validate when passed through the MOD 10 algorithm. You can also generate valid credit card numbers for specific Issuing Networks by utilising their particular prefixes. However, we do not provide you (obviously) with the correspondent verification code for these cards, as they are completely fake and made up randomly.
If you've ever found yourself trying to try a product online which required a credit card, even when you just want to take a look, you know why we made this. We believe there's no need to share such information with providers without the actual intent to buy stuff. Anyone can make a website with a form and require you to insert valuable and sensitive information which requires you to give up your privacy. This is a way to protect yourself in such situations.
The other reason we made this are programmers testing ecommerce websites, applications or other software. They usually need lots of fake data, and this is a very easy way to generate a bunch of valid credit card numbers in a split second. There's another tool for those times when you need to generate all other kinds of data.
The Luhn algorithm or Luhn formula, also known as the "modulus 10" or "mod 10" algorithm, is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers, IMEI numbers, National Provider Identifier numbers in US and Canadian Social Insurance Numbers.github.com
APT: Luhn Algorithm Problem Statement Class 2. number = [1,7,2,3,6] Returns: "YES" The Luhn algorithm generates (from right-to-left) 6 + 6 + 2 + 5 + 1 = 20 which is divisible by 10.You must research how } the Luhn algorithm (also called the mod 10 algorithm) calculates validity and write a method to determine if a sequence of digits stored in an array is valid according to this method.www.cs.duke.edu
My entire answer now can be summed up with this single sentence: You have the factor reversed, you're multiplying the wrong digits by 2 depending on the length of the number. Take a look at the Wikipedia article on the Luhn algorithm. The reason your checksum is invalid half the time is that...stackoverflow.com