Dave wanted to enter a club

Dave wanted to enter a club but a password was required.
So he waited to listen.
A woman appeared the bouncer said 1 and she replied 3, she entered.
A man came the bouncer said 3 the man replied with 5, he entered.
Dave came to the door the bouncer said 5 Dave said 7 but it was wrong.

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Logic :
The password is the number of letters to spell the number said by the bouncer.
So the password for 5 is 4.