I have three ideas about numbers.
First, I think every number has a purpose - otherwise why would a number exist?
Second, I think every number is interesting - even if we haven't yet found out what it's most interesting properties are.
And Third, I think some of the most interesting things about numbers start to occur when they start getting big.
Take 429 for example. I looks kind of plain, and not very interesting. But 429 is really an astonishing number. If you add all of the integers from 4 to 29 you get a total of 429.
But it's not prime, it's not a square, or a cube. It's not even he largest or the smallest astonishing number.
15 is the smallest astonishing number. If you add all of the integers from 1 to 5 you get a total of 15 - kind of neat, isn't it. Next is 27. If you add all of the integers from 2 to 7 you get 27.
Some astonishing numbers work backwards - like 204. If you add all of the integers from 20 (counting backwards) to 4 you get a total of 204. And if you add all of the integers from 21 (counting backwards) to 6 you get a total of 216.
I don't think there is a "largest astonishing number", but the largest one I know about is 891,406,343,154,063.
I won't spoil the surprise by telling you more - you can figure it out.