Character Analysis
Union 5-3992 is described as a "pale boy with only half a brain" (1.18). Apparently he also has regular convulsions. Union 5-3992 was one of Equality 7-2521's classmates in the House of the Students (school), where he was not one of the brightest children. That made him something of an ideal student for the Teachers, because he ran no risk at all of ever distinguishing himself from others or coming off as "superior." It's for that reason that Equality 7-2521, who really is intellectually superior to everyone else in school, tries to imitate him. Later on, they wind up as Street Sweepers together, and work on the same cleaning team of three (with International 4-8818).
You might say that Union 5-3992 is something like the ideal member of his society, for the same reason he was an ideal student for the Teachers. He doesn't take any chances, does what he is told, and has no chance of standing out as an individual. In fact, it's doubtful he could even survive if society weren't there to care for him.