Esri's customer paying between basic($5k/yr) up to enterprise($50k/yr). Each customer pick an organization short name by themself. Also get assigned organization ID.
How many organization short name and ID have you see in this list will give you an idea how much customer Esri currently have.
Esri's entire customer list
https://transparentgov.net/json2tree/esri/hub/static/hub.html?file=hub_v1_created_before_2025_3_26.zip&filter_by=
10 years ago, ESRI use opendata api v3, now ESRI decide to switch to hub api v1,
following are opendata v3 api
US customer only, not include other countries ( default ) from year 2000 to 2025 March
https://transparentgov.net/json2tree/esri/hub/static/opendata.html?file=opendata_v3_region_us_9972.zip&filter_by=
Including all other countries, from year 2000 to 2025 March
https://transparentgov.net/json2tree/esri/hub/static/opendata.html?file=opendata_v3_2000_1_1_to_2025_3_26.zip
opendata api v3 history by year
History records in 2020 only have 8000+
History records in 2019 only have 4000+
opendata api v3 Live
https://transparentgov.net/json2tree/esri/hub/live/opendata.html
hub api v1 Live
https://transparentgov.net/json2tree/esri/hub/live/hub.html
ArcHub https://hub.arcgis.com/search?collection=site
Check hub whether is down or not
https://hubstatus.arcgis.com/