The Meaning of Numbers: The Number 21
Twenty-one symbolizes the great wickedness of rebellion and sin. After the children of Israel left Egyptian bondage they had 21 major rebellious events as their traveled and wandered the wilderness.
The number 13, which symbolizes depravity and sinfulness, and 21 are closely related. The meaning of twenty-one in the Bible is an outgrowth of thirteen. Adding thirteen (sinfulness) and eight (symbolizing a new beginning) gives us twenty-one or a number that represents beginning a new level or effort that is sinful and disobedient against God.
On the last day of God's seven-day Spring festival, the 21st of the month of Nisan, the Eternal carried out his last judgment against the Egyptians. He drowned Pharaoh and his entire army in the Red Sea as they were pursuing the Israelites in order to make them slaves again.
The last day of God's annual Fall Feast of Tabernacles, which occurs every year on the 21st day of the seventh Hebrew month, pictures the end of Christ's 1,000 year reign on earth when the devil is loosed out of his prison for a short time.
Satan's very first task, along with his demons, is to lead people into war and rebellion against all that is Holy. After a short period of time, God executes His final judgment against the Satanic forces by consuming them in fire (Revelation 20:10).
Appearances of the number twenty-one
One of the top ten shortest books in God's word, Obadiah, has only 1 chapter with 21 verses.
Out of 27 New Testament books 21 of them are Epistles.
The book of Hebrews contains materials from twenty-one Old Testament books.
The word Frankincense occurs 21 times in Scripture, as well as the phrase 'the Father.' The names James (the great) and James (the less) also show up 21 times.
The books of 1Kings and 2Kings make a total of 21 references to the sins of Jeroboam (the first king of the Northern Tribes of Israel after their split with Judah). These references were used to show how Israel continued to disobey God even though he gave them plenty of time to repent.
How is the number 21 related to sin?
In 2Timothy 3 the apostle Paul writes of 21 sins which show the exceeding wickedness of self and sin. He begins the chapter with a warning and then starts his list with the words "But know this, that in the last days perilous times will come: For men will . . ."
Selfishly love themselves
Brag quite a bit
Be proud of themselves
Disregard and disobey their parents
Not be thankful for what they have
Reject being holy
Will not have natural affection
Falsely accuse others
Lack any self-control
Will be fierce
Hate anyone who does good
Will act hard-headed
Will have exalted, selfish views
Reject loving God
Will look from the outside as being Godly
On the inside they will deny God's power (2Timothy 3:1 - 4)
Paul's ultimate advice to Timothy, after listing all the above sins, is "turn away from all these" (2Timothy 3:5).
Additional info on Biblical Meaning of 21
The last King of Judah, Zedekiah, began his reign when he was only 21 years old (2Kings 24:18). He was placed on the throne as a 'puppet' king by Nebuchadnezzar of Babylon, who in 597 B.C. conquered Jerusalem and took the then-king Jehoiachin as prisoner. Zedekiah's reign lasted eleven years until 586 B.C., when Jerusalem and its beloved temple were totally destroyed by Nebuchadnezzar.