i want to split the integer into individual elements and add the elements

i made a code to split an integer and add them individually but in some scenario the sum is wrong for example the output expected for 555 is 15 but it shows 16

def find_sum_of_digits(number):
    sum_of_digits=0
    sum=0
    var=0
    #Write your logic here
    while number>0:
        var = number%10
        
        sum += var
        number = number/10
        sum_of_digits=sum
        
    return int(sum_of_digits)

#Provide different values for number and test your program
sum_of_digits=find_sum_of_digits(123)
print("Sum of digits:",sum_of_digits)

The output i want is to add 123 to display 6 and as vice versa to other integer values