TITLE: What is a co-prime?
QUESTION [22 upvotes]: I've never encountered this question in any of my math classes and it just shows up randomly in my comsci class with no further info about it. I've wiki'ed it, but can't even understand that. Could someone explain to me exactly what it is?

REPLY [4 votes]: Two numbers are said to be co-prime if they do not have a common factor other than $1$. For example, the factors of $3$ are $1$ and $3$.