A precise number or population statistic for the galactic population as a whole was never officially given outside of mentioning that the
known parts of the galaxy (like 20% or so) had over roughly 100 quadrillion beings in it (humans and aliens) without counting stuff like the Unknown Regions or Wild Space, so it was probably for the best that they never really go into detail or precise numbers further than that since that usually becomes the source of incredible autism slapfights and history sperging.
The most you were given was population info on specific planets. For example, outside of the hundreds of planets with population info revealed, half of them usually had humans as the "60%" or "100%" of a planet's population (even on alien ones) more commonly than other species, and when that wasn't the case, almost numerous planets had a human presence, either 20, 10 or 1% and when they didn't they would just say "humans and other" or just "other".
However even these statistics were never precise and would change on occasion, even featuring disclaimers at times, like saying they were made from a biased human or alien perspective or due to ignorance or that it was because of inaccurate historical tampering as was the case with contradictions caused by clone wars media like Filoni Wars or related material as seen in the excerpt below:
That way writers wouldn't feel restricted in what they could do creatively or avoid any discrepancies, like forgetting the species or planet grid of a planet. Essential Atlas for example made a lot of mistakes like this which were quickly brought up in the online supplement, or especially when some material tried to find compromises with Filoni Wars which was better off being ignored or only used for superficial info like Jedi Prince was.
Still, based on the most recurring info, half or almost half of the known planets had a large human presence, while the other half were alien-dominated. So humans and near-humans were the most numerous and widespread out of any species, but all aliens when lumped together (all species of non-humans and twileks) seemed to be far more numerous than humans in number, mostly outside the Core Worlds where humans (and partially duros) reigned supreme, but even then they weren't as organized as humans which gave humans an edge in some parts.
Outside of this, some guy on stack exchange once tried to make a rough population measure based on what species is represented most by named characters on wookieepedo, so I wouldn't really put much stock into that statistic.