The number of atoms in a person is almost too big to write out. We just can't imagine that our body is made up of such a big number of atoms that can't even be seen and counted as well.
Of the 7 octillion atoms, we are made of, hydrogen, oxygen and carbon make up about 99%; the other 1% is made up of trace elements.
Keep in mind that the following numbers are based on the number of atoms, not percent of body weight (by weight we are mostly oxygen). A 70 kg. body would have approximately 7*1027 atoms. That is, 7 followed by 27 zeros: 7,000,000,000,000,000,000,000,000,000 - and that's an octillion
And yet we are just a tiny part of the entire universe.