Welcome Ladies and Gentlemen of ATRL to this new Discussion Thread, How Smart Is ATRL?

In this thread I will be posting various questions, riddles and more.
The first person to answer each question will gain points and be added to the leader board.

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Q U E S T I O N S

DIFFICULTY: EASY

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If
1 = 5 ,
2 = 25 ,
3 = 325 ,
4 = 4325

Then 5 = ?