  We calculate the atmospheric neutrino fluxes in the energy range $100$ GeV --
$10$ PeV with the use of several known hadronic models and a few
parametrizations of the cosmic ray spectra which take into account the knee.
The calculations are compared with the atmospheric neutrino measurements by
Frejus, AMANDA, IceCube and ANTARES. An analytic description is presented for
the conventional ($\nu_\mu+\bar\nu_\mu$) and ($\nu_e+\bar\nu_e$) energy
spectra, averaged over zenith angles, which can be used to obtain test data of
the neutrino event reconstruction in neutrino telescopes. The sum of the
calculated atmospheric $\nu_\mu$ flux and the IceCube best-fit astrophysical
flux gives the evidently higher flux as compared to the IceCube59 data, giving
rise the question concerning the hypothesis of the equal flavor composition of
the high-energy astrophysical neutrino flux. Calculations show that the
transition from the atmospheric electron neutrino flux to the predominance of
the astrophysical neutrinos occurs at $30-100$ TeV if the prompt neutrino
component is taken into consideration. The neutrino flavor ratio, extracted
from the IceCube data, does not reveal the trend to increase with the energy as
is expected for the conventional neutrino flux in the energy range $100$ GeV -
$30$ TeV. A depression of the ratio $R_{\nu_\mu/\nu_e}$ possibly indicates that
the atmospheric electron neutrino flux obtained in the IceCube experiment
contains an admixture of the astrophysical neutrinos in the range $10-50$ TeV.
