Simplify the following text for a Grade 8 native English-speaking person.
Original: Chester Alan Arthur ( October 5 , 1829 â `` November 18 , 1886 ) was an American politician and the 21st President of the United States .
Simplified: Chester Alan Arthur ( October 5 , 1829 â `` November 18 , 1886 ) served as the 21st President of the United States ( 1881 â `` 1885 ) .