Robert is a young boy who suffers from mathematical anxiety due to his boredom in school. His mother is Mrs. Wilson. He also experiences recurring dreams—including falling down an endless slide or being eaten by a giant fish—but is interrupted from this sleep habit one night by a small devil creature who introduces himself as the Number Devil. Although there are many Number Devils (from Number Heaven), Robert only knows him as the Number Devil before learning of his actual name, Teplotaxl, later in the story. Scholars argue that the beast cannot refer to Nero because this prophecy was written 30 years after his death. However, some Greek astrologers believe that Nero will be resurrected and reclaim his power.

Paulos, John Allen (18 November 1999). "The Way to Numerical Heaven". The New York Review of Books. 46 (18) . Retrieved 3 September 2011.Are there numbers you avoid in your life? Are you terrified of these numbers enough to develop a phobia? Thuy-Anh Mai, Angie. "Personal Reflections on The Number Devil". Math Horizons. Mathematical Association of America . Retrieved 16 December 2011.

Matsumoto, Valerie J. "Faculty Show Depth, Breadth of the Written Word". UCLA Today. University of California Press. Archived from the original on 4 April 2012 . Retrieved 23 October 2011. Auclaire-Meier, Sebastien. " Der Zahlenteufel. Ein Hörspiel in neun Nächten für alle, die Angst vor der Mathematik haben" (in German). Archived from the original on 26 April 2012 . Retrieved 16 December 2011. Do your hairs stand on end when you encounter the number 13? Your phobia has a name. Prepare to say the tongue twister Triskaidekaphobes (tris·kai·dek·a·pho·bi·a). The association of 666 with evil originates from a passage in the Book of Revelations in the New Testament of the Bible. As it reads in the King James Version (13:18):

a b Pakenham, Michael (11 October 1998). "Does your head need exercise? Here's just the book for you". The Baltimore Sun . Retrieved 3 September 2011. No man might buy or sell, unless he has the market for the name of the beast or the number of his name. Here is wisdom. Let him that has understanding count the number of the beast for it is the number of a man, and his number is 666. All dwelling earth will worship him, whose names have not been written in the book of life of the Lamb slain from the foundation of the world.

In Christianity, 666 is referred to in (most manuscripts of) chapter 13 of the Book of Revelation of the New Testament as the " number of the beast." [1] [2] [3] In mathematics [ edit ]For a time after the fourth night, Robert cannot find the Number Devil in his dreams; later, however, on the fifth night, Robert finds himself at a desert where the Number Devil teaches him about triangular numbers through the use of coconuts. On the sixth night, the Number Devil teaches Robert about the natural occurrence of Fibonacci numbers, which the Number Devil shortens to Bonacci numbers, by counting brown and white rabbits as they reproduce multiple times. By this dream, Robert's mother has noticed a visible change in Robert's mathematical interest, and Robert begins going to sleep earlier to encounter the Number Devil. The seventh night brings Robert to a bare, white room, where the Number Devil presents Pascal's triangle and the patterns that the triangular array displays. On the eighth night, Robert is brought to his classroom at school. The Number Devil arranges Robert's classmates in multiple ways, teaches him about permutations, and what the Number Devil calls vroom numbers ( factorials).