  Using the explicit form of the function to describe the average spectrum of
the extragalactic far infrared background (FIRB) radiation measured by the COBE
FIRAS instrument in the 0.15 - 2.4 THz frequency interval, the radiative and
thermodynamic properties, such as the total emissivity, total radiation power
per unit area, total energy density, number density of photons, Helmholtz free
energy density, entropy density, heat capacity at constant volume, pressure,
enthalpy density, and internal energy density are calculated. The calculated
value of the total intensity received in the 0.15 - 2.4 THz frequency interval
is 13.6 nW m^-2 sr^-1, and comprises about 19.4 % of the total intensity
expected from the energy released by stellar nucleosynthesis over cosmic
history. The radiative and thermodynamic functions of the extragalactic far
infrared background (FIRB) radiation are calculated at redshift z = 1.5.
