mysql sort string number

Quickest, simplest? use * 1

select *
from tbl
order by number_as_char * 1

The other reasons for using * 1 are that it can

1. survive some horrendous mishaps with underflow (reduced decimal precision when choosing what to cast to)
2. works (and ignores) columns of purely non-numeric data
3. strips numeric portions of alphanumeric data, such as 123A, 124A, 125A