According to the Sun Fact Sheet made available by NASA, the luminosity of the Sun is approximately 3.84 * 10^26 joules per second. This is the same as 3.84 * 10^26 watts.
According to the University of Oregon, the luminosity of the Sun is derived by multiplying the intensity of the sunlight received at the Earth by the amount of sunlight that would reach a sphere the size of the Earth's orbit. Counting all wavelengths, the intensity of the sunlight reaching the Earth is approximately 1.4 * 10^3 watts per square meter. A sphere the size of the Earth's orbit has a surface area of 2.8 * 10^23 square meters. Therefore, the luminosity of the Sun is approximately (1.4 * 10^3) * (2.8 * 10^23), or just under 4 * 10^26 watts.