Convert numbers to their English word equivalents and remove non-alphabetic characters.
[CODE]:
```python
def f(x):
    output = ''
    for char in x:
        if char.isdigit():
            if char == '0':
                output += 'zero'
            elif char == '1':
                output += 'one'
            elif char == '2':
                output += 'two'
            elif char == '3':
                output += 'three'
            elif char == '4':
                output += 'four'
            elif char == '5':
                output += 'five'
            elif char == '6':
                output += 'six'
            elif char == '7':
                output += 'seven'
            elif char == '8':
                output += 'eight'
            elif char == '9':
                output += 'nine'
        elif char.isalpha():
            output += char
    return output
```