Are there any prime numbers with more than two digits such that all combinations of its digits (preserving order) are prime? For example, if the number `abc`

is prime, then `a`

, `b`

, and `c`

are prime, and so are `ab`

, `ac`

, and `bc`

.

What is the largest such number, or the largest known? I'm not even sure this is possible, but I imagine the probability of a prime passing this test gets really small really fast as you start adding digits...