I just saw a book with the title “Are Numbers Real?” I didn’t bother reading even the blurb, let alone the book.
Taking into account that I am a philosophy nerd, who likes to consider totally meaningless questions, e.g. “why is there something rather than nothing?” this one is a bridge too far.
To answer the question in the title: yes, numbers are as real as any other abstract concept.
Everything you need to know about numbers comes from just one question: “If you break a rock in half, what do you have?”
The answer: Two rocks.
Uncommon Sense 