Topic: e621 Pronunciation

So this is probably the strangest thing I've ever asked but.... how do you pronounce this "e621"? Is it pronounced like, E. six. two. one.? Or is it, E six hundred and twenty one? Or is it meant to be pronounced together as one word like "essixtuon"?

also, as a side question: why is it called e621?

Updated by Haljkljavahlibrz