text: Check whether the given number is Wagstaff prime or not | Function to check if a number is prime or not ; Corner cases ; This is checked so that we can skip middle five numbers in below loop ; Utility function to check power of two ; Driver Program ; Check if number is prime and of the form ( 2 ^ q + 1 ) / 3
code: function isPrime ( n ) { if ( n <= 1 ) return false ; if ( n <= 3 ) return true ; if ( n % 2 == 0 n % 3 == 0 ) return false ; for ( var i = 5 ; i * i <= n ; i = i + 6 ) { if ( n % i == 0 || n % ( i + 2 ) == 0 ) { return false ; } } return true ; } function isPowerOfTwo ( n ) { return ( n != 0 ) && ( ( n & ( n - 1 ) ) == 0 ) ; } var n = 43 ; if ( isPrime ( n ) && ( isPowerOfTwo ( n * 3 - 1 ) ) ) { document . write ( " " ) ; } else { document . write ( " " ) ; }