Once you give your number on any website that is indexed by google........google automatically caches it.
You can try googling your number and you would probably see the page in cached results.
A friend once put up an advertisement on olx and put my cell number there. I wasn't worried with the spams (its already much) but rather if any employer googles my cell number they would see an awkward advertisement.
I removed the advertisement and still for few months it showed in cache results (yes months).