I didn't realize that the number was anywhere near 2,000,000 people.
The number of crossing the Red Sea may even be greater than
2,000,000. At the time of the event only men were counted according to some scholars. Why women and children were not counted in the Old Testament I can not answer, I'm sure some can however.
There were about 603,000 males between the ages of 20 and 60. Count older and younger males, and then double the figure, and 2 million is extremely plausible, even without counting the Egyptians-masquerading-as-Jews to get out of Egypt (and they were NOT counted, according to the Bible).
This actually could be the wrong number, the actual number could be as many as 4 to 5 million.
When it came to head counting the Hebrews didn't count women and children.