joining or concatenate 2 fields

Thank you in advance for your endless help. You guys are great!

I have 2 cells I want to join. Cell A1 is a "custom" formatted cell that is 7 numbers. I want to add a S in front of that customer formatted field.

Example:

A1 (custom formatted) B1 (text) C1
0000001 s s0000001

I did try to change A1 to numbers but its loosing the preceding 0's. The only way I could keep the number that was present in that column and add the 0's was to do a custom formatting.

I have tried to concatenate them but when I do the 0's are getting removed. What else can I do to get the formatting right?