/*Emirp Numbers An emirp is a prime number that results in a different prime when its decimal digits are reversed. For example, 13 is an emirp number because both 13 and 31 are prime numbers. For example: Input: 17 Output: true (17 and 71 are prime numbers) Input: 113 Output: true (113 and 311 are prime numbers) Input: 23 Output: false (23 is a prime number, but 32 is not) Write a program to check if the user input is an emirp number or not. Bonus: Print all the emirp numbers in a given range.*/ //K137 2019 window.onload = function() { var inp = (prompt( 'Type a number: "17"\nOr a range: "17 113"', '17 113') || '17 113').split(' '); function isEmirp(arr) { String.prototype._reverse = function(str) { var rev = ''; for(var q = str.length - 1; q >= 0; q -= 1) { rev += str[q]; } return rev; } var res = ''; function fillResult(beg, end) { if(beg > end) { var tmp = beg; beg = end; end = tmp; } for(var q = beg; q <= end; q += 1) { var nor = q + ''; var rev = nor._reverse(nor); var isNor = isPrime(parseInt(nor)); var isRev = isPrime(parseInt(rev)); if(isNor && isRev && parseInt(nor) > 10) { res += '# ' + nor + ' is an emirp number. Because ' + nor + ' is a prime number and ' + rev + ' also is a prime mumber.
'; } else { res += '# ' + nor + ' is NOT an emirp number. Because ' + nor + (isNor ? ' is a prime number and ' : ' is NOT a prime number and ') + rev + (isRev ? ' is a prime number.
' : ' is NOT a prime number.
'); } } } if(arr.length == 1) { var a0 = parseInt(arr[0]); if(isNaN(a0)) { res += 'You must input a number or two numbers, separated by space.'; return res; } res += 'Your input is number ' + a0 + '.
'; fillResult(a0, a0); } else { var a0 = parseInt(arr[0]); var a1 = parseInt(arr[1]); if(isNaN(a0) || isNaN(a1)) { res += 'You must input a number or two numbers, separated by space.'; return res; } res += 'Your input is range ' + a0 + ' - ' + a1 + '.
'; fillResult(a0, a1); } function isPrime(num) { if(num <= 1) { return false; } for(var den = 2; den < num; den += 1) { if(num % den == 0) { return false; } } return true; } return res; } document.body.innerHTML = isEmirp(inp); };

isEmirp(num)