In Scripture, numbers are used not only for counting stuff, but also as symbols for or indicators of various Big Ideas.

Many of these numbers are combinations of the two most important numbers, ONE and THREE.
ONE stands for God and all things divine.
I, then, a prisoner for the Lord, urge you to live in a manner worthy of the call you have received, with all humility and gentleness, with patience, bearing with one another through love, striving to preserve the unity of the spirit through the bond of peace: one body and one Spirit, as you were also called to the one hope of your call; one Lord, one faith, one baptism; one God and Father of all, who is over all and through all and in all. [Eph 4:1-6]
THREE stands for God’s actions. E.g., Three visitors came to tell Abraham and Sarah they would have a son [Gen 18], God came down on to Mount Sinai on the third day [Exod 19], and, of course, Jesus rose from death on the third day.
For I handed on to you as of first importance what I also received: that Christ died for our sins in accordance with the scriptures; that he was buried; that he was raised on the third day in accordance with the scriptures. [I Cor 15:3]
FOUR, being ONE (God) + THREE (God’s actions), stands for God’s creative works, both as He created them and as sin distorts them. E.g., in the fourth chapter of Genesis, the first human births are recorded, shortly after which the first human murder is also recorded.
Four appears very frequently in Scripture. It is the number of the great elements (earth, air, fire, and water), directions of compass and wind (north, south, east, and west), divisions of the day (morning, noon, evening, midnight), seasons of the year (spring, summer, autumn, winter), and the phases of the moon (new, waxing, full, waning).
SEVEN, being THREE (God’s actions) plus FOUR (God’s creative works), stands for natural and divine completeness. The Bible is so chock full of sevens, it would be silly to try to quote them here. Click on the link after this quote to see a sampling.
“In the Hebrew, 7 is shevah. It is from the root savah, to be full or satisfied, have enough of. Hence the meaning of the word “seven” is dominated by this root, for on the seventh day God rested from the work of Creation. It was full and complete, and good and perfect. Nothing could be added to it or taken from it without marring it. Hence the word Shavath, to cease, desist, rest, and Shabbath, Sabbath, or day of rest.”
http://www.biblestudy.org/bibleref/meaning-of-numbers-in-bible/7.html
Source
http://catholic-resources.org/Bible/Numbers.htm
http://www.biblestudy.org/bibleref/meaning-of-numbers-in-bible/4.html
http://www.biblestudy.org/bibleref/meaning-of-numbers-in-bible/7.html