It depends on their age. They will have 32 when fully grown but this may not be until they are about 25 or possibly later. But as a child they have 20.
20 teeths
NONE they have beaks
2
Twenty.
about 300 teeth
32 in the adult
20 teeths
4
Variable, and they're called baleen.
Two
because they have life
24 they only loose 20 though they keep their back 4 molars