# Program 12: Factorial
def main():
    n = int(input("Enter number: "))

    fact = 1

    for i in range(1, n+1):
        fact = fact * i

    print("Factorial is:", fact)

main()

Enter number:  3


Factorial is: 6

# Program 13: Reverse Number
def main():
    num = int(input("Enter number: "))

    rev = 0

    while num > 0:
        digit = num % 10
        rev = rev * 10 + digit
        num = num // 10

    print("Reversed number:", rev)

main()

Enter number:  5


Reversed number: 5

# Program 14: Count Digits
def main():
    num = int(input("Enter number: "))

    count = 0

    while num > 0:
        count = count + 1
        num = num // 10

    print("Total digits:", count)

main()

Enter number:  4


Total digits: 1