Men of reddit, how would you react if a woman would give you her phone number?

I ( 20F) decided to write our phone numbers on a piece of paper and if I see someone attractive on the street, on a bus or on a tram, I would give it to him. I don't really know what to say, maybe " hey, you dropped something " or something similar.

I figured my phone number would be better than my Instagram, because it takes a lot more effort for a man to call me, because if he decides to follow me on Instagram, he could stalk me, and a text is much easier and less personal than calling somebody.

So what do you think? Would you be interested if someone did this? And what should I say?