------
## 最终结论
```python
def sum_of_digits(numbers):
    total_sum = 0
    for number in numbers:
        if isinstance(number, int):
            total_sum += sum(int(digit) for digit in str(abs(number)))
    return total_sum

# Test cases
assert sum_of_digits([10, 2, 56]) == 14
assert sum_of_digits([10, 20, 4, 5, 'b', 70, 'a']) == 19
assert sum_of_digits([10, 20, -4, 5, -70]) == 19
```