Convert a RGB colour value to Decimal

Question

How do I convert a RGB colour value to just plain decimal?

So I have: RGB(255,255,255) is white
Its decimal equivalent is: 16777215

I have tried thinking it

Answer 1

var dec = (b & 0xff) << 16 + (g & 0xff) << 8 + (r & 0xff);

(I think that's the correct order for the r,g,b values)

Update

I just checked for browser applications and I got the order wrong, so the correct formula for browsers (read HTML+CSS+javascript) is:

var dec = r << 16 + g << 16 + b;

Assuming r,g,b values <= 255

Other API's may expect a different order for the r,g,b values. I seem to remember at least one that has the order reversed (per my original answer), but I think which one it is at the moment.