Jamieson, Fausset and Brown on Exodus 12:37

37. The children of Israel journeyed from Rameses--now generally identified with the ancient Heroopolis, and fixed at the modern Abu-Keisheid. This position agrees with the statement that the scene of the miraculous judgments against Pharaoh was "in the field of Zoan" [Psa 78:12, 43]. And it is probable that, in expectation of their departure, which the king on one pretext or another delayed, the Israelites had been assembled there as a general rendezvous. In journeying from Rameses to Palestine, there was a choice of two routes--the one along the shores of the Mediterranean to El-Arish, the other more circuitous round the head of the Red Sea and the desert of Sinai. The latter Moses was directed to take (Ex 13:17).

to Succoth--that is, booths, probably nothing more than a place of temporary encampment. The Hebrew word signifies a covering or shelter formed by the boughs of trees; and hence, in memory of this lodgment, the Israelites kept the feast of tabernacles yearly in this manner.

six hundred thousand ... men--It appears from Nu 1:3 that the enumeration is of men above twenty years of age. Assuming, what is now ascertained by statistical tables, that the number of males above that age is as nearly as possible the half of the total number of males, the whole male population of Israel, on this computation, would amount to 1,200,000; and adding an equal number for women and children, the aggregate number of Israelites who left Egypt would be 2,400,000.