Book about a king who becomes immortal

Question

Some time ago I read a book but I can't remember the title or the author. The plot of the book is something like this:

A King is sentenced to death, I don't remember why. I think he runs away and finds a new kingdom where there is a party where one person is elected to be a king and do whatever he wants. He becomes a king again in this party, but the next day he needs to be killed and so he runs away again.

In part of the book he meets the god Pan and his nymphs. Then, he and his wife (I don't remember how they met each other) learn to be immortal living in a cave and doing some kind of yoga exercises.

In another part of the book, the wife's king dies or decides not be immortal anymore and then the king travels to America with the god Pan in a ship, but he is the only one who can see the god. The god has a really strong bad smell and when he is in a place, people have sexual dreams.

Close to the end of the book, he works as a kind of janitor in the university where Einstein works.

Answer 1

Could this be Jitterbug Perfume by Tom Robbins?

As mentioned in the comments, which may be deleted someday, I found this by googling "pan king immortal dreams." Apart from the detail of the ending at Einstein's university, the Wikipedia page lines up with quite a few of the details.

And from the Kirkus Review of the same novel:

we follow King Alobar--a Dark Ages hero--through his global wanderings: he eventually reaches India, meeting a widow named Kudra; both of them are in flight from Death; and both eventually, through the direct intervention of the decrepit god Pan, actually achieve immortality--even learning how to capture the immortality-essence in bottled-liquid form.