Very often, yes. But the sand needs some very expensive preparation first.

(The first step is to turn it into silicon and make large very high quality crystals out of it, which you slice into wafers.)

Real mathematicians write in ancient sumerian cuneiform.

Real mathematicians write in book's margins.

Real mathematicians aren't absolute plebian luddites and manually flip bits in media using a scanning tunneling microscope and electron beam.

Writing is for amateurs