**Table of Contents**show

**Devise a C function that checks whether a given number is prime of not and illustrate its use**

```
#include<stdio.h>
int prime(int n);
int main()
{
int num;
printf("Enter the number to be checked");
scanf("%d",&num);
if(prime(num) == 0)
printf("Number is not prime \n");
else
printf("Number is prime \n");
return 0;
}
int prime(int no)
{
int i;
for(i=2;i<no;i++)
{
if(no%i == 0) // if number is divisible by any number from 2 to n-1
{
return 0;
}
}
return 1;
}
```

**Output**

```
Enter the number to be checked 5
Number is prime
```

**Devise a C function to sum the digits in a number**

```
#include<stdio.h>
int add_digit(int a);
int main()
{
int num, sum;
printf("Enter the number:");
scanf("%d",&num);
sum = add_digit(num);
printf("Sum of digits is: %d", sum);
return 0;
}
int add_digit(int n)
{
int digit, s=0;
while(n!=0)
{
digit = n % 10;
s = s + digit;
n = n / 10;
}
return s;
}
```

**Output**

```
Enter the number:541
Sum of digits is: 10
```

**Devise a c function to reverse the given number**

```
#include<stdio.h>
int rev_number(int a);
int main()
{
int num, rev;
printf("Enter the number:");
scanf("%d",&num);
rev = rev_number(num);
printf("Reverse of number is: %d", rev);
return 0;
}
int rev_number(int n)
{
int digit, r=0;
while(n!=0)
{
digit = n % 10;
n = n / 10;
r = r * 10 + digit;
}
return r;
}
```

**Output**

```
Enter the number:541
Reverse of number is: 145
```

**Devise a C function to check whether a number is palindrome or not**

```
#include<stdio.h>
int rev_number(int a);
int main()
{
int num, rev;
printf("Enter the number:");
scanf("%d",&num);
rev = rev_number(num);
printf("Reverse of number is: %d", rev);
if ( num == rev)
{
printf("\n%d is palindrom", num);
}
else
{
printf("\n%d is not palindrome",num);
}
return 0;
}
int rev_number(int n)
{
int digit, r=0;
while(n!=0)
{
digit = n % 10;
n = n / 10;
r = r * 10 + digit;
}
return r;
}
```

**Output**

```
Enter the number:541
Reverse of number is: 145
541 is not palindrome
```

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