On 2024 Dec, what was the seasonally adjusted M2 money supply in the United States (answer in billions of dollars, rounded to the nearest integer)?

```reference [{"type":"table-json","id":16}] ``` Summary We retrieved the seasonally adjusted monthly M2 money-supply series (code “M2SL”) from the Federal Reserve’s FRED database, then isolated the observation for 1 Dec 2024 and rounded it to the nearest billion dollars. The resulting table shows the U.S. M2 money supply for December 2024 at approximately $21,442 billion .