The dynamics of inertial heavy particles in high Reynolds number turbulence, especially particle clustering, are important fundamental processes, e.g., for raindrop formation in atmospheric flows. To examine the clustering behavior in the turbulence inertial subrange, three-dimensional direct numerical simulations of particle-laden homogeneous isotropic turbulence is performed at resolution 4096^3 for high Reynolds number Re_\lambda = 648 and with 3.2 x 10^9 particles for several Stokes numbers. The results show that the slope of the particle number density spectra at scales in the turbulence inertial subrange is dependent on the Stokes number. It is also observed that the number density spectra in the inertial subrange obey a function of the scale-dependent Stokes number.