I think you can do it very easily by converting your number into a string like this :
your_number = 1234567890
def split_in_3(number):
    number = str(number) # we convert the number into a string
    nb_list = []
    for i in range(2):
        nb_list.append(int(number[:3])) # we take the last three characters of our string and we put them into the list. Don't forget to convert them into integers
        number = number[3:] # we take off the last three digits of the nb and put it in the number variable
    nb_list.append(int(number)) # we add the final part (4 digits) to the list
    return nb_list
print(split_in_3(your_number))
You can return your splited numbers in a tuple or separatly, I did it with a list just as an example