Numbers are imaginary. Does that mean that the concept of "numbers" is not useful or true?
No, numbers are not imaginary. Digits and numerals, which are the way we represent numbers, are imaginary. The numbers themselves are not.
What's a number, then? Can you point to a number in the real world? Where is 2? Where is 4? If you put two apples on a table and say, "There, there is two.", then where is the two? The idea of two separate apples is itself a mental construction: imaginary.
I agree. This is why I have a hard time with math as a concept, I need to be able to learn how something works, why it works, the history of it etc, numbers are simply a construct we came up with as a means to measure the world and communicate, I can't feel or touch a number, it's all in your head.