Htaccess redirect url with database id

I want to redirect this url for each NUMERO in my database:

https://www.website.com/post.php?id=NUMERO

with

https://www.website.com/NUMERO

where NUMERO is the id of a cell in my sql database. For example:

https://www.website.com/post.php?id=7

https://www.website.com/7

To do the redirect I have added in my htaccess file this line:

RewriteRule ^/([0-9]+)/?$ post.php?id=$1 [NC,L] 

But it does not work and I don't undestand why.

Can anyone help me ?