You should better write it this way:
US $ 1000.
In the US, when it is obviously refering to US currency, it is written simply $1000. When there is any possibility that it is in another countries dollars, it is usually $1000 US and I have seen financial documents written elsewhere in which it is written as 1000 USD (apparently their keyboard does not have a "$")
You write 1-1000 as "One to One Thousand."
1000 and another 1000 1000 1000
1000
$1000
1000
x^1000
Write it as in the question!
You write it as 1000.00
1000 = 23*53
3/1000
It is: M =1000