prefixes = {
    'Y':  10**24,    # yotta
    'Z':  10**21,    # zetta
    'E':  10**18,    # exa
    'P':  10**15,    # peta
    'T':  10**12,    # tera
    'G':  10**9,     # giga
    'M':  10**6,     # mega
    'k':  10**3,     # kilo
    'h':  10**2,     # hecto
    'da': 10,        # deka
    'd':  10**-1,    # deci
    'c':  10**-2,    # centi
    'm':  10**-3,    # milli
    'u':  10**-6,    # micro
    'n':  10**-9,    # nano
    'p':  10**-12,   # pico
    'f':  10**-15,   # femto
    'a':  10**-18,   # atto
    'z':  10**-21,   # zepto
    'y':  10**-24,   # yocto
    'Ki': 2**10,     # kibi
    'Mi': 2**20,     # mebi
    'Gi': 2**30,     # gibi
    'Ti': 2**40,     # tebi
    'Pi': 2**50,     # pebi
    'Ei': 2**60      # exbi
}
