1 refers to the unity in the Godhead and is the number of unity. It signifies beginnings and is, in that way, related to the number 8, which starts a thing over. So it reveals that something is new.
2 brings to mind the Father and the Son. Two also has to do with choice. As at the tree of knowledge.
There are two paths or two ways we can choose. It is used in scripture repeatedly to signify "witness."
3 is always a figure of strength and corresponds to 1 in reference to the triune nature of the Godhead.
It is also a figure of resurrection (after "three days" he rose again). It is significant in how it interacts with other numbers derived from it.
4 has to do with all directions in most numerology. For instance, "the four winds." It is global or even cosmic in scope. The cross, having four sides, illustrates the universality and global reach of salvation.
5 in Ephesians stands for church government. This number suggests spiritual governing (apostles, prophets, evangelists, pastors, teachers) and involves nurturing or feeding the flock (Jesus takes 5 loaves and feeds 5,000).
6 stands for man, obviously, and imperfected man at that. Man as "fallen" or not yet at the ideal. It also stands for work, as in 6 days of work. When day 7 arrives the work is over.
7 stands for a number of things like rest and perfection. It is the number of God. It is the ideal, the final perfected state of man. It has the connotation of glory to it, or glorified persons. It also completes a cycle and contains everything. Within the number 7 all is finished and brought to completion.
8 reverts back to 1, like the first day of the week. It is about new beginnings. Eight souls were saved by water in the ark and began the new day.
9 seems to be associated with manifestation, as in traits, like the fruit of the Spirit or the listed charisma. Jesus also uses "99" to denote the status quo, urging his disciples to leave the 99 and go after the 1 stray.
10 is the whole. It signifies a totality. For instance, there are 2 tablets with 5 laws apiece, so there is an agreement (of the horizontal and vertical laws) which govern (5) the people of God as 10, as being complete in themselves. The two (witness) tablets of 5 (government) gives the entire scope of the law. It is the whole counsel of God.
11 would be ten + 1, of course, or a number combining the whole and God, but it doesn't find a particular use in Bible symbology. The original 12 disciples were pared down to 11 until the Book of Acts. It was incomplete in that sense. So, it could be a number of incompleteness that, when combined with 6, for instance, becomes 66 and multiplied by 10 = 666. We then have the number of the incomplete man, fallen and imperfect and his history or existence being completed in six days.
12 stands for the ecclesia, the congegration and the fathers: 12 Jewish fathers, 12 apostles and 12 tribes, or the 144,000 (12 x 12 x 100, which is 10 x 10).
12 + 1 is the foundation or seminal grouping as in Jesus and the 12. 13 is a foundational number. For instance, Arthur and his 12 knights is based on the symbology of the original 13. There is no use of the number as such in the NT.
40 is an important number that denotes testing or a period of examination. 40 days or years in the wilderness. Even its extension to 4,000 is significant in that, biblically speaking, 4 millennia is the testing period from Adam to Jesus in history. 4 (cosmos) x 10 (wholeness) would indicate the completion of a task, in this sense. 40 x 50 (Jubilee, Pentecost) is 2,000, the apparent number of years in a biblical "age."
49 is 7 x 7 which completes a larger cycle than the week. Jesus uses the number in illustrating forgiveness. We forgive 70 x 7, that is, utterly and irrevocably.
50 is the number of Jubilee, denoting restoration and newness of life. The captives are set free. The most significant symbol in this regard is the Jewish Feast of Pentecost which becomes the very day the church was born in 30AD.
1,000 is 10 x 10 x 10, an extension of the whole, or the whole picture. It can be used figuratively or literally. 7 x 1000 seems to be a picture of the whole plan of God, or His entire enterprise focusing on Jesus Christ.
Most other significant numbers one encounters in scripture probably link with these numbers. These are the basic numbers one encounters regularly and my take on their prophetic and symbolic application. I'm sure there's more.