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
behavior with . 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.