  Crystalline membranes at finite temperatures have an anomalous behavior of
the bending rigidity that makes them more rigid in the long wavelength limit.
This issue is particularly relevant for applications of graphene in nano- and
micro-electromechanical systems. We calculate numerically the height-height
correlation function $G(q)$ of crystalline two-dimensional membranes,
determining the renormalized bending rigidity, in the range of wavevectors $q$
from $10^{-7}$ \AA$^{-1}$ till 10 \AA$^{-1}$ in the self-consistent screening
approximation (SCSA). For parameters appropriate to graphene, the calculated
correlation function agrees reasonably with the results of atomistic Monte
Carlo simulations for this material within the range of $q$ from $10^{-2}$
\AA$^{-1}$ till 1 \AA$^{-1}$. In the limit $q\rightarrow 0$ our data for the
exponent $\eta$ of the renormalized bending rigidity $\kappa_R(q)\propto
q^{-\eta}$ is compatible with the previously known analytical results for the
SCSA $\eta\simeq 0.82$. However, this limit appears to be reached only for
$q<10^{-5}$ \AA$^{-1}$ whereas at intermediate $q$ the behavior of $G(q)$
cannot be described by a single exponent.
