Pardon my asking, but the whole idea of domain names is to not have to remember numbers. Why would you want to opt for using the IP number? The only reasons I can think of anyone doing this is for:
A: Your domain has not propagated yet and you want access.
B: Spammers use this technique to make them hard to trace (anonymity from domain whois records).
C: You can't afford a $10 domain name.
Also, if you have shared hosting, you can probably upgrade to a real dedicated IP number for a monthly fee.
On some shared hosting accounts you can access by using the shared IP and appending it with the port number and sometimes the username.
It could look something like one of these, but can be very host specific:
http://123.123.123.123/~username/home/www/
(You probably need the whole path to the shared server root, not jut the root of your account)
or
http://123.123.123.123:82/username/path
(the :82 is a port number)
DeCal is correct that you don't put the .tld on the end of an ip number.