Problem #19

Find the smallest positive integer whose last digit is "6" such that moving the "6" to the beginning of the number increases its value by a factor of 4. For example, the number 1236 would be transformed to 6123, which is more than four times as large, while 3126 becomes 6312, which is less than four times as large. You are to find a number which is transformed to one exactly four times as large.