# C#: Project Euler Solutions to Problems 21 and 52

http://projecteuler.net/problem=21

Evaluate the sum of all the amicable numbers under 10000.

```int totalsum = 0; for (int num = 1; num < 10000; num++) { int tempsum = 0; for (int i = 1; i < num; i++) { if (num % i == 0) tempsum += i; } int secondtempsum = 0; for (int i = 1; i < tempsum; i++) { if (tempsum % i == 0) secondtempsum += i; } if (secondtempsum == num && num !=tempsum) { Console.WriteLine("amicable pair " + num + " , " + tempsum ); totalsum += num; } } Console.WriteLine(" Final sum : "+totalsum);```

http://projecteuler.net/problem=52

It can be seen that the number, 125874, and its double, 251748, contain exactly the same digits, but in a different order.

Find the smallest positive integer, x, such that 2x, 3x, 4x, 5x, and 6x, contain the same digits.

```static void Main(string[] args) { long count = 1; while (true) { long initnum = count; long t2 = initnum * 2; long t3 = initnum * 3; long t4 = initnum * 4; long t5 = initnum * 5; long t6 = initnum * 6; if (compareNums(initnum, t2) && compareNums(initnum, t3) && compareNums(initnum, t4) && compareNums(initnum, t5) && compareNums(initnum, t6)) { Console.WriteLine(initnum); break; } count++; } }   public static bool compareNums(long a, long b) { string initstring = "" + a; string doublestring = "" + b; bool found = false; foreach (char digit in doublestring) { foreach (char innerchar in initstring) { if (innerchar == digit) found = true; } if (!found) return false; found = false; } return true; }```