When we write numbers in English we use commas where continental European countries often use points, and points where continental Europeans use commas.

So, for example, while many continental Europeans would write 45.678,90 (forty-five thousand, six hundred and seventy-eight and 90/100), native English speakers would write 45,678.90.

That’s easy – and I hope you already know it.

Now, here’s the main point of this post.

I often see numbers written like this: 19.456 thousand or this: 19,456 thousand
Neither is correct in English, and both may cause confusion.

In English we do not mix numerals and words unless we are using the words “million”, “billion”, “trillion” etc. So, it is wrong to write, e.g., 24 thousand; instead you should write 24,000 or twenty-four thousand. But it is correct to write, e.g., 56 million.

19.456 thousand or 19,456 thousand should therefore be written in English in either of the following ways:
19,456,000 (read as “nineteen million, four hundred and fifty-six thousand”)
19.456 million (read as “nineteen point four five six million”)

I’m sure you’ll appreciate the possibility of confusion when a number written
19.456 thousand should be understood as 19.456 million.