I'm looking for an easy way to assign a post number to each post in wordpress and display it out of the total number of posts. A little info:

1. There will be about 100 "posts", each on its own page
2. I want users to click through each post, so start at post 1 and click "next post" to get to post 2
3. I want it to say post 4/100 at the top for each post
4. I want the URL to have the post name in it

I was going to use WP-PageNavi and set each page to display 1 post, however I need the url to show /post-name/ and not /page/2/

I know I can count total number of posts pretty easily, any idea how I can assign a number to each post without having to do it manually? I'd like to sort by date added.