40 Days?

40 days is a sort of leitmotiv in the Tanakh: e.g. when God purified Earth with water, He caused it to rain 40 days and 40 nights (Genesis 7:12).Moses was on Mount Sinai for 40 days and 40 nights ( Exodus 24:18 ). Moses interceded on Israel’s behalf for 40 days and 40 nights ( Deuteronomy 9:18, 25 ). The Law specified a maximum number of lashes a man could receive for a crime, setting the limit at 40 ( Deuteronomy 25:3 ). The Israelite spies took 40 days to spy out Canaan ( Numbers 13:25 ).Goliath taunted Saul’s army for 40 days before David arrived to slay him (1 Samuel 17:16). When Elijah fled from Jezebel, he traveled 40 days and 40 nights to Mt. Horeb (1 Kings 19:8).

Does the number 40 have some specific meanings according to gematria? Does Kabbalah teach us something about the esoteric value of this number?