An E2 Search with "ignore exact" for keyword Everything will give you a truncated list of all nodes by node_id. This is because E2 search filters out the keyword Everything and hence matches all nodes, then list the nodes by order of node_ids.

From that list, it seems the smallest publicly accessible node_id is 101, and most other regular node_ids are from 10158 and above.

However, secret nodes shows there are more interesting secret nodes below node_id 101 and up to node_id 10158.

Also, a search for superdocs via Everything Document Directory indicates that E2 reserves the 3 digits node_ids for important nodes.