Multiply by                        For    Power   Symbol1
---------------------------------------------------------
1,000,000,000,000,000,000,000,000  yotta    24     Y
    1,000,000,000,000,000,000,000  zetta    21     Z
        1,000,000,000,000,000,000  exa      18     E
            1,000,000,000,000,000  peta     15     P
                1,000,000,000,000  tera     12     T
                    1,000,000,000  giga      9     G
                        1,000,000  mega      6     M
                            1,000  kilo      3     k
                              100  hecto     2     h
                               10  deka      1     da
                               .1  deci     -1     d
                              .01  centi    -2     c
                            .00,1  milli    -3     m
                        .00,000,1  micro    -6     μ2
                    .00,000,000,1  nano     -9     n
                .00,000,000,000,1  pico    -12     p
            .00,000,000,000,000,1  femto   -15     f
        .00,000,000,000,000,000,1  atto    -18     a
    .00,000,000,000,000,000,000,1  zepto   -21     z
.00,000,000,000,000,000,000,000,1  yocto   -24     y

One "attoboy" sure isn't worth much!

Notes: 
1.  Taken from http://www.pleacher.com/mp/mfacts/numnotat.html.
2.  Greek letter mu.