Is the Marvel Comics "Sandman" an Immortal?

Or at least as Immortal as physically possible? While many "Immortal" characters in Marvel Universe seem to be able to be killed SOMEHOW, But Sandman, by his very nature, seems to be an oddity. Theoretically, you could freeze him, them throw him into the Sun, and as long as his "Soul Particle" remained, he could reform.

And since this "Soul Particle" is essentially indestructible, even able to remain after full on molecular change, wouldn't that make HIM indestructible?

The only thing that could actually kill him, would be something capable of Erasing Matter entirely (not just changing its form).