  Monthly averages of the sunspot number visible on the sun, observed from
  1749, Zurich Observatory, and from 1848 other observatories, have been
analyzed. This time signal presents a frequency power spectra with a clear
$1/f^\alpha$ behavior with $\alpha\simeq 0.8 \pm 0.2$. The well known cycle of
approximately 11 years, clearly present in the spectrum, does not produce a
sensible distortion of that behavior. The eventual characterization of the
sunspot time series as a fractal is analyzed by means of the detrended
fluctuation analysis. The jump size distribution of the signal is also studied.
