Numbers in the thousands are expressed in figures with a comma and can never be a combination of figures and words.
...sent 45,000...
...received 133,000 of them...
...offered 50,000 for it...
Whether the number is said "fifteen hundred" or "one thousand five hundred," the
comma is inserted.
...sent 1,500...
...received 3,400...
...offered 2,100...
Happy punctuating!
Margie