Approached a girl but dont know if she is interested

So my buddy and I went to some art festival thing downtown. I approached two girls with no problem. Talked to them and what not. Maybe for 2 minutes max. As I talked to them or asked them questions, they laugh before responding. Does this mean they are being flirty or did I do something wrong?

I even got the girls number. Usually when approaching I dont pay attention to anyone around me. After I got her number I noticed a group of guys saying ahhhhhh like I totally scored. My friend even said they were tape recording.

But that doesn't matter because when I text her I got no response. So the first question is why they laugh before responding and how can I go further after getting the number?