in this video https://www.youtube.com/watch?v=AbgcITHmXBI the guys in the end says that there are more atoms in a grain of sand than stars in the (observable) universe. My estimation with this:100 bilions of galaxies100 bilions of stars per galaxy
So, 10000 bilion of bilions of stars in the observable universe=$10^{22}$
For a typical grain of sand (size 1mm) made of Si02 , the estimate is $10^{19}$ atoms... If a grain is a fraction of mg, 1 g of grain has truly more atoms than stars in the universe.
Do you have some good estimate?