Actually there are 17,678,577,670 ants in the world.
Today, more than 12,500 species are classified with upper estimates of about 22,000 species. (Wikipedia) For the source and more detailed information concerning your request, click on the related...
22,000 species
between 20 and 30. :)
there are more than 500millon ants on the world but you do step on them every day.