Christina aguilara's voice is how many octaves?

It has been said that Christina Aguilera has four octaves exactly. Other sources report that she has climbed out of that going even a little further such as four octaves and a half. She has a lower register. The belting register, the falsetto, and the whistle register. She hardly ever uses the whistle register notes as you can recall in some live performances or even recorded sessions. Some artist may have more octaves than Christina may have, but she has more power in the ones that she does have.