The Sun's apparent magnitude as viewed from Earth is about −26.74. Apparent magnitude measures how bright an object looks from Earth, and its reversed logarithmic scale means that more negative numbers indicate brighter objects.
The Sun appears vastly brighter than any star because it is both intrinsically luminous and extremely close by cosmic standards: sunlight takes about 8 minutes 20 seconds to reach Earth. For comparison, Sirius, the brightest star in Earth's night sky, has an apparent magnitude of about −1.46. The full Moon is roughly −12.74, still far dimmer than the Sun.
The quoted solar value is a standard approximate figure rather than an unchanging constant. Earth's orbit is slightly elliptical, so the Sun appears a little brighter near perihelion, when Earth is closest, and a little dimmer near aphelion. Apparent magnitude should also not be confused with absolute magnitude, which compares how bright objects would appear if placed at the standard distance of 10 parsecs.