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

+ (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]

+ The current score to beat in King Kong's Prime Numbers Game. Note that 28 is a perfect number.

(There are 2 curios for this number that have not yet been approved by an editor.)

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