starguy wrote:
how can I reverse the characters of cells.

(data) (should be)
12345 54321
2456 6542
asdf fdsa
23 32

any formula which can do this?

If you know the maximum size of the string in a cell (I shall assume 16)
then:

=MID(A1,16,1)&MID(A1,15,1)&MID(A1,14,1)&MID(A1,13, 1)&MID(A1,12,1)&MID(A1,11,1)&MID(A1,10,1)&MID(A1,9 ,1)&MID(A1,8,1)&MID(A1,7,1)&MID(A1,6,1)&MID(A1,5,1 )&MID(A1,4,1)&MID(A1,3,1)&MID(A1,2,1)&MID(A1,1,1 )