The question was how many (number) not names?
In that case surely the Egyptians said somewhere how many there were?
There are whole books/dictionaries of Egyptian deities eg Budge, and Mercatante.
(The Hittites had something like a 1000 gods.)
Perhaps as many as the stars...?
Like the 75 names Ra, all goddesses said to be emanations/manifestations of Isis. I think similar is said about Neter? and I once saw an Egyptian version of I am that I am in New Dawn but lost it.
A good split thread/topic from this would be one on Numbers. A starter list (not exhaustive):
1 - all goddesses = Isis;
2 - Hor vs Set; pyrs Giza; lands; rivers (UE,LE)/caverns; mtns (Bahu,Manu); banks;
3 - Atum,Shu,Tefnut; Khepri-Ra-Atum; Ptah-Seker-Osiris; pyrs Giza; "dyns" Manetho; triads/trinites;
4 - sons Horus; children Geb&Nut; yrs Siriadic;
5 - days epact; children Geb&Nut;
7 - Cleopatras; Hathors;
8 - gods Ogdoad;
9 - gods Ennead; days tempest Shu/Arish; bows/arcs;
10 - god-kings; bows/arcs;
12 - sections Tuat;
13 - months;
14 - kas Ra; pieces Osiris;
22 - nomes;
30 - dyns Manetho; hebsed/jubilee;
36 - decans;
42 - books Thoth; negative confesions;
60 - 2x60=henti/Osiris;
75 - names Ra;
110 - perfect old age;
400 - crowphoenix;
500 - phoenix;
900 - Moeris-Saite;
1100 - books Thoth;
9000 - Atlantis; Ptah;
I would be interested to know more about the "42 original stand alone deities"?
Interestingly it is the minor gods names that usually provide missing links (cognate correspondences) between pantheons of different cultures/languages.
A list (of main deities) of mine would include (excluding doubles/spilts like Horus, Horemkhu, Harpocrates, Harakhty; and male/female same names):
Aelurus, Amon, Aton, Amt, Anukis, Anubis, Abtu, Af-Ra, Anhur, Anit/Anat, Apis/Hapi, Apophis/Aahpehti/Akhekh, Ash, Aso, Amsu, Atum, Auka, Babi, Bast, Bata, Bennu, Bes/Bek, Bar/Baal, Bahudet, Buchis, Dedun, Dua, Ekhi, Gom, Hesat, Heket, Heh, Hathor, Horus, Hershef, Hu, Iusas, Isis, Itum/Nefertum, Imhotep, Khnum, Khanm, Khepri, Khonsu, Kherty, Khem, Kek, Khenti-Amenti, Kneph, Mendes, Min, Mau, Mut, Maat, Montu, Merwer, Nebertcher, Nephthys, Neith, Nun, Naunet, Narh, Neter, Nekhebet, Nu(p)t, Nubti, Osiris/Busiris, Ptah/Egyptus, Par, Pakhet, Pharaoh, Phra, Qeb/Keb/Seb/Geb, Quades, Ra/Re, Rat, Reret, Ranno, , Reshef, Sati, Selkit, Se(p)t/Set(h)/Sutekh, Sais?, Serapis, Sed, Sobek, Sia, Sekhmet, Seker, Sopedu/Sopdet, Shehtu, Tat, Tefnut, Tenen, Thoth, Tanit, Taurt/Taweret, Unno/On, Unt, Upuaut, Wadj Wer, Wadjet/Uto/Buto, Wennefer, Wosret, Yah/Aah/Iahu, Yamm, .