You can do it with something like this:

10 k=mtop-1000 : rem k base index into RAM
15 FOR c:=0 to 4:rem number of digits
20 N=int(number/10); rem N chr, parsed offnumber
25 number=number-N*10:N=N+31
30 xby(k+c)=N :rem memory location K+c now contains N
40 Next

-ish its only a rough outline

God its a long time since I wrote BASIC, my head hurts.

Steve