Is a 550watt power supply safe to power a Phenom x4 9650 and a GTS250 graphics card?

It might be, but it will depend on what other things are in your computer. Remember that the power supply runs everything in the PC. And the more stuff you have in there, th (MORE)

Is 20449 a prime number?

A prime number has only 2 factors which are 1 and itself. Composite numbers are everything else except 1 and 0. 1 and 0 are neither prime, nor composite. 20449 is composite.