Why is he keeping my number?

1) You broke up with someone a month ago.
2) He didn't respond to your message.

It seems pretty clear to me that he doesn't want to talk to you. I don't see why anything else matters.

Just drop it and move on.

The reason why I am questioning this is that. With whatsapo if you don't want to be contated by someone you either block the person or you remove their number from your phone but he hasn't done any of it.

Maybe he can't be bothered to look for your name on the app.

Some of us don't take keeping/deleting a name from an app that seriously.

If it bothers you to see his name, you can delete it in your app.

In order to talk to someone on whatsapp you need to add them to your phone not the app. I don't understand people. If you don't want to talk to someone, don't keep their number. It's that simple.

It's not that simple at all.

I just checked... I have the number of an ex-girlfriend from 3 years ago because I never bothered to delete it. She hasn't called me in 3 years. I haven't called her. No big deal.

The way you can be sure that he doesn't want to talk to you is that he didn't respond when you sent him a message. That's it. Whether or not he takes the time to delete your number is his business, not yours.