I avoid "fake folder levels that are meaningless".
You have this URL:
http://www.example.com/deals/How-to-get-50-off-blue-widgets/732226
The final folder level implies that you might have other valid URLs like:
http://www.example.com/deals/How-to-get-50-off-blue-widgets/123456
http://www.example.com/deals/How-to-get-50-off-blue-widgets/654321
http://www.example.com/deals/How-to-get-50-off-blue-widgets/482935
which will also be valid.
I prefer the number at the front.
I use all lower case.
I never use underscores as separators.
I don't know the structure of the rest of the site, but I would likely change the deals folder to a 'd' prefix (and other folders to similar 1 or 2 letter prefixes):
http://www.example.com/d732226-how-to-get-50-off-blue-widgets
The 'd' prefix is used to quickly match the correct rewrite (and quickly reject the others, at the first character). The number and the words are then extracted and passed to the PHP script. The PHP script must look in the database to see if record 732226 exists. If it does not exist, send 404 HEADER and "include" the HTML file with the human-readable error message. If 732226 exists in the database, extract the "name" from the database and compare it with the requested name. If it is not an exact match, send a 301 HEADER and redirect to the correct URL (using the requested number and the name as extracted from the database). If the requested name does match the requested number, serve the content.
The above technical steps are vital. They prevent Duplicate Content issues and avoid the site being flagged for "soft 404" problems.
The front-loaded number also allows corrupted URL requests such as
http://www.example.com/d732226-how-to-get-50-otrert5y65widgertfcvgybhunjimhbgvf
and shortened URL requests such as
http://www.example.com/d732226-how-t
to be processed, redirecting to the correct URL.
Indeed, you effectively also have your own URL shortener and can post URLs such as
http://example.com/d732226
elsewhere knowing they will work just fine, redirecting to the correct URL.
You'll run into many people that say "put the number at the end, you need the words first for 'better SEO'". I don't believe it makes all that much difference. However, having the numbers at the front leads to better rewrite efficiency (faster pattern matching) and better functionality (redirecting corrupted and shortened URLs).
This topic has come up several times so far this month. There may be additional useful details in those other threads.