What does the numbers in the URL of a post stand for?

[tomleung1996]

Each URL of a post has a series of numbers after the equal sign,like this one below:
https://bitcointalk.org/index.php?topic=2881736.0

I know these numbers might be time-related, but I don't know the details, they don't seem to be timestaps or maybe they are just the IDs in the database?

And I found that:
1) if you simply find a topic number and plus one each time, you won't always go to a latter post, sometimes end up with error (maybe nobody post at that moment?)
2) number after the dot sign decides the replies that show to you (if the number is 20, then you will get the first 20 replies. if 40, you will get 20th to 40th)

[bitperson]

Are you sure they're not simply sequential numbers? The smallest one available seems to be https://bitcointalk.org/index.php?topic=5. Perhaps the fact that some topic IDs return an error might be due to removed topics.

[Husires]

Yes it's consecutive but for the whole forum.
You can not view all posts due some limits " Trashcan,deleted,...etc".
Check out the latest replies you'll find in sequence:
use this "Show unread posts since last visit. or bitcointalk Pull the page down"

1.https://bitcointalk.org/index.php?topic=2381688.msg29635996;topicseen#msg29635996
2.https://bitcointalk.org/index.php?topic=2799783.msg29635995;topicseen#msg29635995
3.https://bitcointalk.org/index.php?topic=2664406.msg29635994;topicseen#msg29635994
4.https://bitcointalk.org/index.php?topic=2826150.msg29635993;topicseen#msg29635993