1 - One God
2 - Male and Female, bride and bridegroom, a couple
3 - The signature of God (such as: God the Father, Son & Holy Spirit)
4 - The signature of Nature, Creation (such as: North, South, East, West)
5 - The signature of God's mercy and grace.
6 - The signature of imperfection, sin, disobedience.
7 = 3+4 - The signature of Totality. Signed by God and Nature. Used repeatedly in the book of Revelation.
8 - Every male circumcised at 8 days of age (Genesis 17:12, Luke 2:21).
9 - Fruit of the spirit (love, joy, peace, patience, kindness, goodness, faithfulness, gentleness and self control--Galatians 5:22-23).
10 - Signature of Worldly Power. Completeness. 10 fingers, 10 toes.
12 = 4x3 - The signature of God's People. Nature multiplied by God. Such as: the 12 tribes of Israel & 12 Apostles.
20 - Age of responsibility. Able to be counted as a member of the army (Numbers 1:45, 26:2).
30 - Age of maturity. Jesus started ministry at 30 years of age (Luke 3:23).
40 - A generation. 40 years in the wilderness (Numbers 14:33-34). Several of the judges and kings in the Old Testament reigned either 20 or 40 years, rained 40 days (Genesis 7:17 ), Jesus fasted 40 days (Matthew 4:2).
50 - Year of jubilee. Leviticus 24:10
70 - Desolation to last 70 years (Jeremiah 29:10 and Daniel 9:3).
120 = 12x10 - God's people times worldly power. The maximum life span of people (Genesis 6:3).
144 = 12x12 - The signature of God's people in the heavens multiplied by God's people on earth. All of God's people.
490 = 70x7 - Amount of time to bring in everlasting righteousness (Daniel 9:24).
666 - Total imperfection, sin, disobedience. The mark of the beast (Revelation 13:18).
1000 = 10x10x10 (103 or 10 to the third power) - Worldly power raised by the power of God. Highest power (completeness?).
144,000 = 144x1000 - All of God's people times all the powers in the universe. Absolute completeness!
Note: A 1000 years to human kind is like a day to God (Psalm 90:4 & 2 Peter 3:8). A time scale of 365,000 to 1. Thus an hour to God is like 41.67 years to human kind. And a half hour to God is like 20.83 years to human kind.