"Mole Day"...6.02 x 10^23

Today could be considered "Mole Day". "Mole Day"? We celebrate a rodent? No. Not that kind of "mole" but rather Amedeo Avogadro's [nineteenth-century Italian physicist] discovery that a mole of any gas contains the same number of atoms or molecules, which happens to be 6.02 X 10^23.

Amedeo Avogadro

Avogadro constant