This depends on the context, whether it be in the world, or for a particular country. See related questions:
US: The US has had 45 Presidents (44 unique people), with Donald Trump being the 45th president.
there were 43 presidents
44
1
How many presidents have lived in the White House.
there were 44 presidents in U.S.A.
33 presidents
21 presidents
they are be 44 Presidents in the U.S.A.
Ghana as a nation has had many presidents. Ghana so far has had about 14 presidents. The research is still but in progress but so far Ghana as had 14 presidents.
Indonesia had 7 presidents
0
8 presidents