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!
I hit four thousand followers.
This is the only tofu in the world created by China with great 4000 years of history.
I love you so much that I could knock down four thousand telephone poles at once.