Yes there is such thing as two thousands in a number.
The two is in the ten-thousands place value.
Two thousandths of an inch is written 0.002"
Within the range covered by "thousands" would be any number from 1000 to 99,000 - after that the range is "hundreds of thousands. However, there is no such thing as "the biggest number" as all numbers can be added to, again and again, to an unreachable infinity.
$51,200
666
There are twenty-three thousand, with two hundred remaining.
8672300
In 557,995 the number 7 is in the thousands column. Start from the right and work to the left, the number places are units, tens, hundreds, thousands, ten thousands, hundred thousands.
5.0203
60.251
Technically, it's the same thing but it's still considered to be rounded to the nearest thousand. 259,678 to the nearest thousand is 260,000
The number two is a singular, common noun, word for a thing.