I am looking for a category of natural numbers (about <1000 is enough) with its properties.
Here's some examples :
2 - It is the first prime number.
1729 - It is the smallest number expressible as the sum of two cubes in two different ways.
Here's some bad examples that I don't focus on :
36 - It is the number that its half is equal to multiplying each digits (3 and 6 in this case).
69 - It is the number which has a sexual meaning.
36 is the bad example because it depends on the base 10.
Is there any site about this?
http://www.numbergossip.com/69 (for example). Please see thread https://math.stackexchange.com/questions/921/interesting-numbers-in-maths