The number 12 in scripture is the number of Israel.
There are 12 tribes in Israel. An interesting thing happens in the many listings of the tribes. Because Joseph gets a double blessing from his father Jacob (Israel), one tribe is always omitted in the list of 12. The omissions in this case are the teaching point of the list.
Revelation 7 gives the number of them which were sealed of the children of Israel during the tribulation. There are 12,000 from each tribe of the 12 tribes listed totalling 144,000. These are clearly Jews and are not Jehovah Witnesses, Seventh Day Adventists, the Church (Spiritual Israel as they are sometimes called), British Israelites or any other group who can’t understand what it means to be a part of the 12 tribes of Israel and read on a third grade reading level. The tribe of Dan is missing here because of their history of idol worship. Another interesting thing in this list is that Joseph is substituted for his son, Ephraim. Hosea says that Ephraim is given to idols, leave him alone. There is a good chance that the Anti-Christ and the False Prophet come from these two tribes in some part of their genealogy.
There are 12 “the kingdom of heaven is like” parables because the kingdom of heaven as listed in Matthew has to do with Israel. This should be contrasted with the 7 “the kingdom of God” is like parables listed in Mark and Luke which have to do with the Church.
There are 12 apostles which will judge the 12 tribes of Israel.
If you know the symbolic meaning behind the number 12 (Israel), you may understand some scripture passages a little differently. For example, Mark 5 contains an account of a woman who had an issue of blood for 12 years and Jesus healed her and also an account of a 12 year old girl who Jesus raised from the dead. Jesus healed Israel’s issue of blood (see Hebrews 10:4) and will raise Israel up again at the end of the tribulation (notice it is verse 42 when the girl is raised, see also Job 42 for the cross reference).