Its interesting. When I first encountered complex numbers when starting high school it was very difficult to wrap my head around how they could be actual numbers.

I no longer have that problem, ever since I truly understood how all numbers are simply abstract tools for reasoning. In a way, it's interesting that complex numbers seem more "real" than the real numbers themselves.

I remember listening to a radio show where a physicist discussed the link between quantum mechanics and complex numbers, and thus how they were fundamental to reality [1], whereas we don't know whether real numbers actually describe physical reality.

[1] If I remember correctly, one argument was that although a common use of complex numbers is an alternative number system for making trigonometric/polar calculations simpler, they underpin quantum mechanics in a way that cannot be alternatively formulated in terms of real number numbers

A lot of physics equations describe real quantities like E=mc2. We just kind of take it for granted. You can formulate quantum mechanics without complex numbers but they seem kind of fundamental to it in a similar way to how real quantities like energy seem fundamental to reality.