def number_to_html(number_as_string):
    """usage as ``number_to_html(num2str(1.023e-12)) == "'-1.0 x 10<sup>-12</sup>'"``"""
    s = number_as_string
    if s.find('e') > 0:
        if s.startswith('1e') or s.startswith('-1e'):
            s = s.replace('1e', '10<sup>')
        else:
            s = s.replace('e', ' x 10<sup>')
        s += '</sup>'
    return s
