  We report a detection of a 0.153 days period in the classical nova V1674 Her
using the NICER observations taken within a month since the outburst (i.e.,
about MJD 59405). The X-ray period is consistent with the orbital period
previously found in the optical band, strongly suggesting the NICER signal as
the X-ray orbital periodicity of the system. A seemingly double-humped profile
was obtained by folding the detrended X-ray light curve with the period after
removing the rotational X-ray pulsations of the nova. The profile may be caused
by occultation by the companion or the accretion disk, possibly indicating a
high inclination of the system. The gamma-ray emission of V1674 Her with a
significance level > 5 sigma was detected by Fermi-LAT close to its optical
peak and the emission faded away within 1 day, which is the shortest duration
known for a gamma-ray nova. Folded on 0.153days, a marginal gamma-ray
variability can be also seen in the LAT light curve, but without the
double-hump feature observed in X-rays. If the gamma-ray modulation is real,
its origin is probably different from that observed in the X-ray and optical
bands.
