Furthermore, 45 is also triangular, which means:

45² = (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9)² = 1³ + 2³ + 3³ + 4³ + 5³ + 6³ + 7³ + 8³ + 9³ (don’t ask me how that one works I only know how to prove it by induction)