Here's why we will never run out of 16-digit credit and debit card numbers 

Americans have, on average, more than three credit cards each. Many also have debit cards, flexible spending cards and other accounts that are all associated with a unique 16-digit number that enables transactions.

Plus, most popular virtual payment methods now use so-called tokenization, which means that there are additional unique numbers tied to your account. Each card you have loaded into Apple Pay, for example, is tying up three 16-digit combinations, since the watch and phone each use a unique tokenized number.

"We have way more card account numbers than we ever did before," said Heather McGuire, senior program manager for CO-OP Financial Services, which helps credit unions leverage technology. "You could potentially have four or five different 16-digit account numbers tied to one account."

Ongoing data breaches mean that firms are re-issuing thousands of cards every year and some have also begun issuing different account numbers to joint account holders in order to reduce replacement costs after breaches.

With all of these new numbers, is it possible that we'll eventually run out of unique numbers to use

"This [question] comes up every few years," said Kris Carrera, senior vice president, financial services product development, global retail payments, at FIS, a financial services technology firm. "But we're not going to run out."

The potential 16-digit credit card combinations provide far more account numbers than could ever be used, according to Cris Poor, a mathematics professor at Fordham University. Poor says the 16-digit card numbers has a quadrillion possibilities.

By comparison, the world population is a mere 7.7 billion.

"So each person in the world could have more than a million potential credit numbers, and I don't know anybody who has anywhere near that many credit cards," Poor said.

To understand why we're not going to run out of numbers, you need to know how the distribution of credit card numbers works.

All card numbers guidelines are laid out by the International Organization for Standardization and the American National Standards Institute, which also sets standards around things such as the size and shape of credit cards. The first digit signifies the network and industry, so for example, all Visas start with a "4," while AmEx cards start with a "3." That allows the merchants to identify who is ultimately responsible for payment of charges.

The first digit, along with the five that follow it, are collectively known as the Bank Identification Number, or BIN. They're assigned to the individual payment networks (Visa, MasterCard, etc.), which then distribute them to card issuers (Bank of America, Wells Fargo, etc.).