Catalyzes the reduction of NADP(+) with F420H(2) via hydride transfer, and likely the reverse reaction, i.e. the reduction of F420 with NADPH. Probably functions in the regeneration of NADPH required in biosynthetic reactions. Is specific for reduced F420 as electron donor for the reduction of NADP; neither reduced FAD nor FMN can act as electron donor. The enzyme is also specific for NADP; NAD is not utilized as substrate. NADP(+) + reduced coenzyme F420-(gamma-L-Glu)(n) = 2 H(+) + NADPH + oxidized coenzyme F420-(gamma-L-Glu)(n) Optimum pH is 8.0. Optimum temperature is 60 degrees Celsius. Is extremely thermostable. No detectable activity is lost when the enzyme is incubated at 65 degrees Celsius for 4 hours. Homotetramer. Belongs to the F420-dependent NADP reductase family.