Big deal you say? Strike the initial 3 off. The remaining number is also prime. Continue striking them off, one at a time. All the remaining numbers are also prime. The number above is the largest of the "left-truncatable primes", of which there are precisely 4260. How do I know? I wrote a program to find them (took only about 10 minutes in Python) and you can verify them on this webpage. This sequence is also A024785 in the Online Encyclopedia of Integer Sequences. You can also generate the list of right-truncatable primes (where each prefix is prime). There are only 83 of those, with the largest number being 73939133.
Apparently a pretty serious pet food recall is underway. I caught this on the news, and since I'm such a softie for the well being of pets, I thought I'd give some more information here (it was difficult to find on my local tv news channel news website). Apparently wet and pouch style cat and dog food manufactured by menufoods.com can cause kidney failure. Menufoods is a supplier to many other pet food suppliers, even fairly upscale ones like Iams, so if you have any questions, you should check out the Menufoods website to see if you could have any food which might be affected.
Luckily, I've always fed Scrappy dry cat food.