Guessing the meaning of a number

Suppose I give you an n-digit number and ask you what it represents. This seems impossible, and in theory it is impossible. But in practice it’s often possible. Apps on a phone may automatically interpret a 10-digit number as a phone number or a 16-digit number as a package tracking number. And very often these interpretations are correct, given the kinds of things most people use their phones for. It’s not surprising that a 10-digit number on a phone is a phone number. It’s more interesting that a 16-digit number is likely a tracking number. It could be other things, such as a credit card number. But people don’t usually write out credit card numbers in a text note; credit card numbers likely saved in some more opaque way. I run into a variation of this problem routinely, trying to infer what a number represents inside medical notes. A five-digit number could be a US postal code, or it could be a medical procedure code. A six-digit number could be a date in MMDDYY format, or it could…