def phred_number_to_letter(score):
    """Simple function to turn a PHRED score from number to letter. That's it.

    :param score: PHRED score number
    :type score: int
    :return: Returns just PHRED score (Illumina 1.8+, I believe) 
        letter corresponding to the numeric score
    :rtype: str
    """
    return chr(score+33)