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The quasar 1641+39 is a relatively nearby and fairly bright source. In the blue band, it has exhibited variability with a very large amplitude, changing between magnitudes 14.7 and 17.7. Variability is a common phenomenon for quasars; however, a variation of 3 magnitudes is a rather rare event. Taking this variability into account, spectral studies produce the following picture (Fig. 1). From Fig. 1 it can be seen that there is some variability even in the radio range. The spectral index is close to 0.4, which represents a fairly steep spectrum for quasars, although the variability does not allow the spectral index to be estimated accurately.
The quasar 1641+39 is a very active and highly compact source, while the spectral index suggests that it is embedded within a larger-scale radio source. In the region surrounding the quasar within a radius of 6 degrees, the number of quasars is 1973 which is relatively high, and the redshift histogram shows that the maximum number is concentrated in the range z = 1.5–2. A detailed study of the histogram makes it possible to conclude that this distribution pattern supports the idea that the quasars are distributed uniformly within the 6-degree-radius region. The relatively small number of detected quasars at low redshifts is due to the scarcity of nearby quasars, while at high redshifts the smaller number is mainly caused by the difficulty of detecting them.