GCD.py

import math 
n1 = int(input("Number1 ->"))
n2 = int(input("Number2 ->"))
print (math.gcd(n1,n2)) 

# or

def gcd(n1,n2): 
    if(n2==0): 
        return n1 
    else: 
        return gcd(n2,n1%n2) 

Palidrome.py

n = input("Number -> ")
if (n == n[::-1]):
  print("Yes")
else:
  print("No")

reversing_a_number.py

a=int(input("Enter ->"))
final = ""
for i in list(str(a))[::-1]:
  final += str(i)
print(int(final))

Sum_of_digits.py

n = 123
sum = 0
for i in str(n):
  sum += int(i)
print(sum)