He would be 108.
I had forgotten it was his birthday til a moment ago but was actually listening to my audiobook of "People of the Black Circle" whilst taking the kids to school.
Weird Tales Magazine, the original publication of many of his best stories, posted a great tribute with loads of sword swinging art and several of REH's poems this morning here.
and a final thought...
I cannot express enough how much moving to LA just barely makes me feel this way ~