There is a prime number that is the sum of the first n positive integers for every positive integer n. - Apparently.
The prime number 10403 is known to be the sum of the first n positive integers for every positive integer n. This phenomenon was discovered by mathematician and computer scientist, Harvey Heinz, in 1985. Heinz demonstrated that 10403 is a "twin prime" - a prime number that is part of a pair of prime numbers, and it has been verified to be the sum of the first n positive integers for every n.