You can automatically number your blog posts ordered by the post date. You can automatically put the post number in front ofyour blog post title. All you need is install and activate Auto Numbering Post. It needs no other configuration options to set.
As soon you activate it, it immediately starts showing your blog post number on each and every blog post of your WordPress site. Even it shows the post numbers in Recent Posts and all other related widgets for displaying post links on your sidebar.