It's taken a year or so, but I use (don't ask why) the opening note of Coronation Street (a British soap) that is a C note , the major 3 of Ab. Every time I walk past a piano - several times a day, I hum that note, then play it to check (much to my wife's amusement and disgust). Just done it now, and got in the crack to one side of the correct note. Getting better but not perfect yet. So, yes, it can be learnt. Obviously. Some have perfect/absolute pitch, but we mere mortals put up with relative pitch, where we get a note and can pitch another from it. Again, a skill to be practised.
With tuners as small as they are,or using a mobile, you could carry one around, and try a note every so often. It may take time, but it's a good way to bore your friends.
50 yrs ago - pre tuners, during caravan holidays, I used to drop a house key on a hard surface to keep guitars in 'concert pitch'.Daft, but it worked !