TITLE: Mathematicians who were late learners?-list
QUESTION [112 upvotes]: It is well-known that many great mathematicians were prodigies. 
Were there any great mathematicians who started off later in life?

REPLY [31 votes]: Preda Mihailescu is a good example http://en.wikipedia.org/wiki/Preda_Mihăilescu.
He received his PhD with 42, and proved the Catalan conjecture 5 years later.
The Catalan conjecture was open for 160 years.
He proposed in 2009 a proof of the Leopoldt conjecture, but I am not sure about the status of this.