It is equal to the ideal gas constant divided by Boltzmann's constant, as well as the Faraday constant divided by the elementary charge, and it can also be considered a conversion from microscopic units like atomic mass units to grams.
Using the kinetic gas theory, its value was first approximated by Loschmidt, and it is still sometimes called the Loschmidt number in Germany. Jean Baptiste Perrin gave it its current name and estimated its value using Brownian motion, but modern methods of calculating it rely on x-ray diffraction. It is equal to the ideal gas constant divided by Boltzmann's constant, as well as the Faraday constant divided by the elementary charge, and it can also be considered a conversion from microscopic units like atomic mass units to grams. FTP, what is this number of atoms in 12 grams of carbon-12, named after an Italian chemist, and given the approximation 6.022 x 1023?
Using the kinetic gas theory, its value was first approximated by Loschmidt, and it is still sometimes called the Loschmidt number in Germany.
Avogadro's number [accept Avogadro's constant; prompt on the numerical answer]