QBASIC Program to display prime digits of a supplied number

REM QBASIC Program to display prime digits of a supplied number
Declare Sub Disprime(n)
CLS
INPUT n
Call Disprime(n)
End
Sub Disprime(n)
m = n
PRINT "Prime digits are ";
WHILE n <> 0
r = n MOD 10
c = 0
n = n \ 10
FOR i = 1 TO r
IF r MOD i = 0 THEN c = c + 1
NEXT i
IF c = 2 THEN PRINT r
WEND
End SUB