If everyone spoke the same language, would numbers exist?Watch
Ironically most the world uses the Arabic characters for numbers: 1,2,3,4,5 etc. nowadays.
Used to be Roman numerals but we all know what happened to the Roman Empire
To answer your question, yes numbers would still exist, although if we have a single unified language, I would assume we would all conform to either Roman or Arabic numerals, whether the unified language came from Latin or Arabic.
However, numbers are valued/useful in some societies, and less useful in others. So, some societies would make more frequent use of them, and others would make less frequent use of them, and higher numbers might be considered to be jargon-esque.
In the same way, there is probably some remote, mountainous community whose largest industry is llama trading. Those people will talk about ideas that are highly specific to their llamas, e.g. hoof problems that arise frequently when climbing a certain hill, spitting distance, fur matted in a certain type of mud, unusual coat colours that are valued by neighbouring communities. They will have their own terms to identify those things, where we would have to compound words to talk about these things.
Similarly, we talk about racecars, tyre treads, motorways, horsepower, paint jobs, etc. Those are ideas that theoretically could be discussed in our hypothetical llama society, but they might find it more troublesome to come up with the words, because they don't use them day to day.
Essentially, cultural differences are just one place where dialectic variations can arise. But I don't want to go too much into this, because there are plenty of factors.
If you're curious, maybe you can have a look at John McWhorter's The Language Hoax. It's a book, but he explained the concept in a YouTube video pretty succinctly.