How to ORDER BY lexigraphically?

[admin]

I'm using mysql.

SELECT * FROM mytable ORDER BY inv_num;

inv_num is an integer field. I need it to be sorted in numerical order...but it's not. If i have more than 9 items i get:
1
10
11
2
3
4
5
...


Is there anyway to get my query results sorted properly when they are returned?