The nth Prime Page will now find any of the first 2.623˙1015 primes or π(x) for x up to 1017.
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!+1)/(28+1) is a prime with 28+1 digits. [Silva]
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.
Fn2-28 is never prime, where Fn denotes the n-th Fibonacci number. [Poo Sung]
28 is a perfect number expressible as the sum of first five nonprime numbers, i.e., 1 + 4 + 6 + 8 + 9 = 28. [Gaydos]
(There are 4 curios for this number that have not yet been approved by an editor.)
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