Supposedly, Visa owns all the ones. Mastercard owns like half of the fives, but no one owns the rest of the fives. Amex only owns two of the threes, JCB would seem to own the rest, but they have different lengths, which puts them in different address spaces. Diners' Club and Carte Blanche used to own a number of the threes, but they've been subsumed by Mastercard, and they were 14-digit cards anyway. Also, Visa has both 16-digit and 13-digit cards, so that gives them two distinct address spaces, one of 10 quadrillion and another of 100 billion. Discover actually does own only 6011, but no one owns any other sixes.