There's going to be more sophisticated answers on the top level, I'll just weigh in because my perspective might be moderately relevant (I study History at a German university). I'd like to stress that nobody who wants to be taken seriously in scientific debate would argue that this number is somehow substantially too high. If the math feels absurd, the reason is that this was an atrocity on an absurd scale.
If I take your question / post title literally, the answer is "yes". To capture the reality of what happened in the Holocaust, it is not "absurd" but rather too low. The iconic number of six million refers only to the number of Jews killed in the Holocaust. It makes sense to remember this number because Jews constitute the largest number of victims and because their "extinction" was so central to Nazi ideology as a whole. However, the number doesn't take into account millions of other groups of victims who also died by the hundreds of thousands: Romani, people from the occupied territories in Eastern Europe who were deemed racially inferior by the Nazis (Ukrainians, Poles, Russians...), political enemies of the regime (often regardless of wether they were actively working against the regime or not - this includes communists / socialists, social democrats, trade unionists - especially during the early and mid-thirties), Jehova's witnesses, homosexuals, transgender people and those with disabilities or genetic disorders who were considered "lebensunwertes Leben" ("life unworthy of life").
All in all, the number of people killed systematically during the Holocaust and more or less systematically in all kinds of mass executions and other atrocities against mostly civilian populations is far, far higher than six million, not even taking into account the victims of the actual war (civilian deaths in the Soviet Union alone number well over ten million by most estimates, I think the most common number is somewhere around 19 million) - I wanted to point that out because your title links the death of the European Jews to World War II, which of course isn't completely incorrect, but keep in mind that dying in the Holocaust was substantially different from dying "in the war" as a civilian or soldier.
One more thing about the number of Holocaust victims. As I said, I'm sure somebody else will make a top-level comment with actual sources, I was trying to tell you that while your question might be in order in the context of this subreddit, the number (at least the scope) is not seriously debated in Historiography. And while new sources may alter the exact number the discipline works with, you were certainly not "been fed propaganda", despite what Holocaust deniers and revisionists might want to tell you. Take two of the "classics" of Holocaust research for example:
Raul Hilberg's "The Destruction of the European Jews" from 1961 (not technically the first, but often called the "seminal" study of the Holocaust, well over 1,000 pages) contains an estimate of just over 5 million Jewish victims.
Lucy Dawidowicz's "The War against the Jews" from 1975 comes up with just over 5,9 million victims.
These two authors had a lot of conflict going on between them, as Dawidowicz ignored Hilberg's study despite it being an important contribution to her area of research. At that time, two schools of explaining the Holocaust (look up "intentionalists" vs. "structuralists" if you're interested) stood against each other in often heated debates. However, despite all differences, the number of Jews who died in the Holocaust was not estimated to be substantially lower than at least four million (mostly over five or around six million, though). A lot of things about the Holocaust have been seriously debated - intention, collaboration and resistance, the extent to which the general populace knew about it - but the claim of "propaganda" regarding the number of victims is not one you'll hear serious historians use.
And if you like direct source material that is definitely unsuspicious in regards to "propaganda", consider the words of Dr. Wilhelm Hoettl during the Nuremberg Trials. He (in)famously quoted Adolf Eichmann with the number of six million Jewish victims during interrogation. His statement is often cited in relevant literature, you can look it up here.
Hilberg, Raul: The Destruction of the European Jews, New Haven 1961.
Dawidowicz, Lucy: The War against the Jews, New York 1975.