The simple statistical model statement relating the yield YP of fission fragments to the effective neutron binding energy , namely YP α exp(−/T), can be used as a basis for parallel developments, one leading to the well-known empirical delayed-neutron statement where Y is the number of delayed neutrons per fission. Repeating the development for prompt neutron emission leads to the analogous result where is the prompt neutrons per fission. This semi-empirical result implies that a semi-logarithmic experimental plot of against (3Z - A) should be a family of straight lines. Currently available experimental results justify this prediction. The theoretical precision of this semi-empirical formula is estimated to be ±10% or better, depending mainly on the part and shape of the fission yield-mass curve taken into account. The existence of the above empirical and semi-empirical formulas strongly suggests that the yield of fission neutrons, as well as their spectrum, can be calculated by using the standard statistical model with non-adjustable parameters.