Prime Curios!: 28

28
(another Prime Pages' Curiosity)

Curios:

Curios Search: Participate:

The second perfect number. Leonhard Euler (1707--1783) proved that all even Perfect numbers are of the form 2^n-1(2ⁿ - 1) where 2ⁿ - 1 is a Mersenne prime M_n.

(28#)² + 29 are consecutive primes. [Luhn]

28 is a perfect number expressible as the sum of first five prime numbers i.e., 2 + 3 + 5 + 7 + 11 = 28. [Gupta]

The number of Hadamard matrices of order 28 is prime. [Rupinski]

The 28th Fibonacci number plus and minus 28 is prime, i.e., F(28)-28 and F(28)+28 are primes. [Opao]

(28!+1)/(28+1) is a prime with 28+1 digits. [Silva]

The 28th Fibonacci number plus 28²⁸ is prime. This is the largest such number less than a thousand. [Opao]

28!+28^28+1 is prime. [Silva]