S.I. Prefixes for International Units of Measurement.

        yotta [Y] 1 000 000 000 000 000 000 000 000     = 10^24
        zetta [Z] 1 000 000 000 000 000 000 000         = 10^21
        exa   [E] 1 000 000 000 000 000 000             = 10^18
        peta  [P] 1 000 000 000 000 000                 = 10^15
        tera  [T] 1 000 000 000 000                     = 10^12
        giga  [G] 1 000 000 000                         = 10^9
        mega  [M] 1 000 000                           (a million)
        kilo  [k] 1 000                               (a thousand)
        hecta     100                                 (a hundred)
        deca      10
                  1
        deci      .1
        centi [c] .01                                 (a hundredth)
        milli [m] .001                                (a thousandth)
        micro [u] .000 001                            (a millionth)
        nano  [n] .000 000 001                          = 10^-9
        pico  [p] .000 000 000 001                      = 10^-12
        femto [f] .000 000 000 000 001                  = 10^-15
        atto  [a] .000 000 000 000 000 001              = 10^-18
        zepto [z] .000 000 000 000 000 000 001          = 10^-21
        yocto [y] .000 000 000 000 000 000 000 001      = 10^-24

Note the 'u' for micro should really be the Greek letter known as 'mu'