What could be a valid process ID on a Linux system?

On a Linux system, process IDs (PIDs) are numerical identifiers assigned to processes when they are executed. Valid PIDs can range from 1 to a maximum value that is determined by the system's configuration, typically up to 32768 or higher depending on the implementation.

The number 21398 is within the commonly acceptable range for process IDs on most Linux systems. It is a valid PID because it is a positive integer and falls within the bounds that the Linux kernel uses to manage processes.

While the other numbers, such as 8080, 467, and 2000, could in theory also serve as valid process IDs since they are all positive integers, the way the question is structured suggests a consideration of typical or contextually valid IDs that have been observed in practice, where the choices vary in likelihood. However, without the specific context or constraints provided in the question, 21398 stands out as a clear representative of a valid PID that typically could be found in use on a Linux system.