As of March 2023, TSA said [1]: "TSA PreCheck® application program has surpassed 15 million active members" and "Thirty-two million travelers now benefit from TSA PreCheck expedited screening after being vetted though TSA PreCheck ®, U.S. Customs and Border Protection’s Global Entry or another federal vetting program."
As of September 2023, CBP announced stated that there were over 12 million Global Entry members in a press release. [2]
This appears to include SENTRI and NEXUS members, since as of July 2022 it was stated: [3] "There are over 7.6 million participants enrolled directly in Global Entry, and over 1.8 million members of NEXUS and SENTRI that also receive Global Entry benefits."
[1] https://www.tsa.gov/news/press/releases/2023/03/02/tsa-prech...
[2] https://www.cbp.gov/newsroom/national-media-release/cbp-anno...
[3] https://www.cbp.gov/sites/default/files/assets/documents/202...
When you enter customs upon re-entry to the US there's a sign for a place where they'll do your interview real quick before letting you go. The downside (IIRC) is that you don't get your number for precheck either until you do this, so if you only do international travel 1-2 times per year you might want to find an interview time.
But, then again, I lucked out - TSA came to my work and did interviews there. Kind of weird but it got me in with little hassle.
Well you're in luck - it's not TSA that interviews you, it's CPB!