The function counts the occurrences of the digit '1' in the input strings containing only digits and returns the count in words. If the input string does not contain any digits or contains alphanumeric characters, the function returns an empty string.

[CODE]: 
```python
def count_digit_1(input_string):
  if input_string.isdigit():
    count = input_string.count('1')
    number_to_word = {0: 'zero', 1: 'one', 2: 'two', 3: 'three', 4: 'four', 5: 'five', 6: 'six', 7: 'seven', 8: 'eight', 9: 'nine'}
    return number_to_word.get(count, 'count not in range')
  else:
    return ''
```

Let's test this hypothesis with a few more examples.

COMMAND: PYTHON(./temp/function.py "11" "111" "2112" "3210441" "22")