Answer:
Indonesia
Step-by-step explanation:
Indonesia is the country with the most Muslims, over 88% of the population is Muslim like the clue said.
It is located at 5 degrees south and 120 degrees east and made up of 17,508 islands, which is more than 17,000.
It is close to the equator.
Indonesia matches this description very well.
Hope you understood and have a nice day!! ;D