Create a Python program that calculates the sum of the digits of a European Union VAT number.
DE1905303456
vat_number = "DE1905303456"

vat_number_without_check_digit = vat_number[:-1]

sum = 0
for c in vat_number_without_check_digit:
 if c.isdigit():
 sum += int(c)

print(f'Sum of digits: {sum}')