How old do you think are beloved hedgehog is, Sonic the hedgehog?!?!!Cause..what the hell do you think?(Lol)

Some say In the originL sonic series or just the sonic series he is normally 15, some say in video game series, he is 21, some say in all any or both sonic series he is 21 or 15.
So SON!!
Like I said in the question , what the hell do you think?(Lol)