  We analysed the combined data of sunspot groups from Greenwich
Photoheliographic Results (GPR) during the period 1874-1976 and Debrecen
Photoheliographic Data (DPD) during 1977-2017 and determined the monthly mean,
annual mean, and 13-month smoothed monthly mean whole sphere sunspot-group area
(WSGA). We have also analysed the monthly mean, annual mean, and 13-month
smoothed monthly mean version 2 of international sunspot number (SN) during the
period 1874-2017. We fitted the annual mean WSGA and SN data during each of
Solar Cycles 12-24 separately to the linear and nonlinear (parabola) forms. In
the cases of Solar Cycles 14, 17, and 24 the nonlinear fits are found better
than the linear fits. We find that there exists a secular decreasing trend in
the slope of the WSGA-SN linear relation during Solar Cycles 12-24. A secular
decreasing trend is also seen in the coefficient of the first order term of the
nonlinear relation. The existence of ~77-year variation is seen in the ratio of
the amplitude to WSGA at the maximum epoch of solar cycle. From the pattern of
this long-term variation of the ratio we inferred that Solar Cycle 25 will be
larger than both Solar Cycles 24 and 26. Using an our earlier method (now
slightly revised) we predicted 127 (plus or minus 26) and 141 (plus or minus
19) for the amplitude of Solar Cycle~25. Based on ~130-year periodicity found
in the cycle-to-cycle variation of the amplitudes of Solar Cycles 12-24 we find
the shape of Solar Cycle 25 would be similar to that of Solar Cycle 13 and
predicted for Solar Cycle 25 the amplitude 135 (plus or minus 8), maximum epoch
2024.21 (March 2024) plus or minus 6-month, and end epoch 2032.21 (March 2032)
plus or minus 6-month with SN ~4.
