Four Thousand
numeral
You have four and you have thousand. Multiply them together and you have four thousand.
This is a jukugo word, which usually means on'yomi readings from the kanji. That's true for the 千 part, but the 四 reading is kun'yomi. You should know how to read this word as long as you've been studying your kanji!
四千円
four thousand yen
四千キロ
four thousand kilos, four thousand kilometers
四千ドル
four thousand dollars
フォロワーが四千人になりました。
I hit four thousand followers.
この山は、およそ四千メートルです。
This mountain is about 4000 meters tall.
四千円で他人の心は、かえないよ。
You can't buy someone's heart for 4,000 yen, you know.