How to get else option that prints out ("This is not a number"). Strings and Ints HELP! (ValueError: invalid literal for int() with base 10:)

ERROR MESSAGE: ValueError: invalid literal for int() with base 10:"

Thanks

# Name
name = input("Enter Name: ")
# Age
age = int(input("Enter Age: "))

if age == str():
    print("Not a Number!")
else:
    pass


# Age - 100 equals
subage = 100 - age

# Take the result of previous expression and add to year.
age100 = subage + 2020

# Print out results

print(name,"! " "You will be 100 years of age in the year of: ", age100)

just writing more so i can get this thing to post. sdfsdff sfsdf