Hundred
It's a landmark for a young child to count to 100; it sort of covers all the "ordinary" numbers. One hundred is obviously significant for other groupings: 100 cents is a dollar; 100 yards is a touchdown; 100 years is a century, and the landmark for a very long life. It makes sense, then, that in the Bible, 100 represents fullness or a state of completion, or in some instances simply "much." For instance, people marvel that Abraham had Isaac when he was 100 years old; the number represents the point at which the Lord, when growing up as Jesus, united the human elements of himself with the divine elements and in a sense became "complete.
Genesis 12:1-3
1
Now Yahweh said to Abram, "Get out of your country, and from your relatives, and from your father's house, to the land that I will show you.
2
I will make of you a great nation. I will bless you and make your name great. You will be a blessing.
3
I will bless those who bless you, and I will curse him who curses you. All of the families of the earth will be blessed in you."