Shell programs for prime and palindrome

Shell scripting programs to implement whether a number is prime as well as a program to check for a palindrome. If you have any doubts please let me know 

PRIME

#!/bin/bash
echo " enter a number"
read n
i=2
flag=0
while((i<=$n/2))
do

((c = n % i))
if ((c==0))
then
flag=1
fi
((i=i+1))
done
if ((flag==0))
then
echo "prime"
else
echo "composite"
fi

PALINDROME

echo “enter a string to be entered:”

read str

echo

len=`echo $str | wc –c`

len= ((len-1))

i=1

j= ((len/2))

while((i<j))

do

k=`echo $str | cut –c $i`

l=`echo $str | cut –c $len`

if((k!=l))

then

flag=1;

fi

((i=i+1))

((len=len-1))

Done

If((flag==0))

then

Echo “palindrome”

Else

Echo “ not palindrome”

fi