What is Barack Obama's presidential order number?

Barack Obama is considered the 44th President of the United States.

He is the 43rd person to serve as US president, although his presidency is the 44th. President Grover Cleveland served two non-consecutive terms and, therefore, was both the 22nd and 24th President, making it add up to 44 presidencies with 43 presidents.
He is the 44th US President, Serving from 2009 to 2017.
He is the 44th President.