Prompt
Create a realistic portrait of David Hilbert, a renowned German mathematician, sitting in a study with a book in his hand, surrounded by papers and mathematical equations. He should be dressed in formal attire, with a suit and tie, and have a thoughtful expression on his face. In the background, there should be a blackboard or a chalkboard with some of his famous equations, such as those related to Hilbert space or Hilbert's problems, written on it. The style should be reminiscent of a classic oil painting from the early 20th century.