Minimal Prime/Examples

857 is a minimal prime in base 10 because there is no prime > 10 among the shorter subsequences of the digits: 8, 5, 7, 85, 87, 57. The subsequence does not have to consist of consecutive digits, so 149 is not a minimal prime in base 10 (because 19 is prime and 19 > 10). But it does have to be in the same order; so, for example, 991 is still a minimal prime in base 10 even though a subset of the digits can form the shorter prime 19 > 10 by changing the order.