Oracle SQL Developer 19.2.1 contains several known vulnerabilities (CVE‑2020‑2982, CVE‑2019‑2904) related to bundled libraries (Jython, Jackson). Use only on isolated development networks.
To understand the "1921" request, you have to go back to 2019. Oracle shifted its naming convention to align with the year. "19c" stands for Calendar Year 2019. sql developer 1921 hot download for windows
Downloading and Installing Oracle SQL Developer 19.2.1 on Windows Oracle SQL Developer 19