Let n = 2 0 1 9 ! . Find the number of prime numbers that exist between n + 2 to n + 2 0 1 9 .
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If we take a general case: n + k , where k = 2 , 3 , 4 . . . 2 0 1 9
n = 2 0 1 9 ! = 2 0 1 9 ( 2 0 1 8 ) . . . . . ( k ) . . . . ( 2 ) ( 1 )
∴ we can express n + k as k ( k 2 0 1 9 ! + 1 ) , where k = 2 , 3 , . . 2 0 1 9 which is divisible by k . So no prime numbers exist between n + 2 and n + 2 0 1 9 .
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Interesting extension: There are 2 2 known n for which n ! + 1 is prime ( 2 0 1 9 is not one of them). It is conjectured (but still an open question) that there are infinite such n .
See Factorial Primes