"144,000" would not be written that way back 2000 years ago. The highest number was 1000 then, so any number higher than that would have to use multiples. However, there's no need to take that number literally because there's a way to break that down so one can see the likely, imo, "message" inside.
Because of the above, the most logical breakdown would be like this: twelve twelves thousands. That's awkward to us today because we don;t speak that way.
So, why "twelve"? It was a number associated with "completion", therefore a good number. How many tribes of Israel? How many apostles? etc. But notice "twelve" is repeated, so what does that say? Probably "completion upon completion"-- iow, very complete.
"Thousand" was the highest number then, and it was often used to symbolize numbers beyond our comprehension. Here in the States, if I see a large flock of birds outside, I might say to you "Look, there's a million birds out there!". Now, I really don't expect you to start counting them. To our early Jewish ancestors, "thousand" said much the same, and one may note how many times it's used in the scriptures, sometimes in combination with other numbers.
So, if we put this together, what is this saying? It's "completion upon completion with greater numbers than we can imagine". But does this make sense in the context of the scriptures? Yes, and it deals with the "numbers" of those converting to the Way.
Is this the correct interpretation of 144,000? Of course there's no way to tell for sure, but it does make sense in the above context.
BTW, this was not my idea but of some theologians that are familiar with this on both the religious and cultural scale.