How many Israelites?

Exodus 1:9 says, “And he said unto his people, Behold, the people of the children of Israel are more and mightier than we:

1:10 Come on, let us deal wisely with them; lest they multiply, and it come to pass, that, when there falleth out any war, they join also unto our enemies, and fight against us, and so get them up out of the land.”  Egypt was a series of cities and towns built along the Nile River.  How could they possibly outnumber the Egyptians. Exodus 1:5 says, “And all the souls that came out of the loins of Jacob were seventy souls: for Joseph was in Egypt already.”  To go from 70 to possibly hundreds of thousands would be a little much n my eyes.