Question

who was the only bachelor president?

Answer 1

A bachelor means:
"A man who is not and has never been married."
Throughout the United States presidents there has only been one that fits this classification.
James Buchanan is the one.
Although he was engaged, but the lady broke it off...

Answer 2

James Buchanan, Jr. (English pronunciation: /bjuːˈkænən/; April 23, 1791 – June 1, 1868) was the 15th President of the United States (1857–1861). He is the only president from Pennsylvania and the only president who remained a lifelong bachelor

Answer 3

Buchanan.