There are 26 gods in gayatri mantra:
tat – ganesh
sa – Narasimha
vi – vishnu
tu – siva
va – krishna
re – radha
Ni – lakshmi
yam – agni
bha – indra
Rgo – saraswati
dE – durga
va – hanuman
sya – prithvi
dhee – surya
ma – Sriram
hi – seetha
dhi – chandra
yO – yama
ya – brahma
na – varuna
chO – hayagreeva
da – hamsa
yaat – tulasi
Gayatri mantra should be chanted 1008 times; one can chant 108 times too. Alternatively for arthgyan it can be chanted 21 times, for moksha, it can be chanted 25 times, for money gain, it can be chanted 30 times.
Gayatri has fire in face, brahma the creator in forehead, vishnu the protector in heart and Siva the destroyer on top of head. So its a combination of all Gods. Gayathri Manthra can be chanted 3 times a day.
Goddess Gaythri confers the boon of Intelligence as Gayathri, Protection as Savithri and Learning as Saraswathi. Gayathri is therefore called Sarvadevata Swarupini.