Ok this has always bothered me in scifi shows, movies etc. Where they will either look for or try to send prime numbers to show or find intelligence. So they go and tap out the numbers "Morse code" ...

Meet the new largest known prime number. It starts with a 4, continues on for 23 million digits, then ends with a 1. As is true with all prime numbers, it can only be evenly divided by one and itself.