terviknumbers

A terviknumber is a term used in recreational mathematics to describe a specific type of integer. A positive integer is called a terviknumber if it is divisible by the sum of its digits. For example, the number 12 is a terviknumber because the sum of its digits is 1 + 2 = 3, and 12 is divisible by 3. Similarly, 18 is a terviknumber since 1 + 8 = 9, and 18 is divisible by 9.

The term "terviknumber" is not a standard mathematical term found in formal literature. It appears to be a neologism, possibly coined for a specific puzzle, game, or online community. These numbers are also known by the more established name, Harshad numbers or Niven numbers, after the Indian mathematician D. R. Kaprekar and the Dutch mathematician Ivan Niven, respectively.

The sequence of terviknumbers begins with 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 18, 20, 21, 24, 27, 30, 36, 40, 42, 45, 48, 50, 54, 60, 63, 70, 72, 80, 81, 84, 90, 100, and so on. All single-digit numbers are terviknumbers as the sum of their digits is the number itself, and any number is divisible by itself. The existence of an infinite number of terviknumbers is a proven mathematical fact.