  We report on a multiwavelength survey of a sample of 42 flat-spectrum
radio-loud narrow-line Seyfert 1 galaxies (RLNLS1s). This is the largest known
sample of this type of active galactic nucleus (AGN) to date. We found that 17%
of sources were detected at high-energy gamma rays (E>100 MeV), and 90% at
X-rays (0.3-10 keV). The masses of the central black holes are in the range
$\sim 10^{6-8}M_{\odot}$, smaller than the values of blazars. The disk
luminosities are about 1-49% of the Eddington value, with one outlier at 0.3%,
comparable with the luminosities observed in flat-spectrum radio quasars
(FSRQs). The jet powers are $\sim 10^{42-46}$ erg s$^{-1}$, comparable with BL
Lac Objects, yet relatively smaller than FSRQs. However, once renormalized by
the mass of the central black hole, the jet powers of RLNLS1s, BL Lacs, and
FSRQs are consistent each other, indicating the scalability of the jets. We
found episodes of extreme variability at high energies on time scales of hours.
In some cases, dramatic spectral and flux changes are interpreted as the
interplay between the relativistic jet and the accretion disk. We conclude
that, despite the distinct observational properties, the central engines of
RLNLS1s are similar to those of blazars.
