My Number

The lottery number, my preferred number, the date of my birthday, my pin code ... Determine if a number is pretty or ugly is relatively complicated. As an aesthetic evaluation, always enters the field of subjectivity and tastes of each. This time Adolfo Quirós Gracian, a professor at the Autonomous University of Madrid and vice president of the RSME, provides an answer to this mathematical challenge. In this case, a number look nice if it meets exactly one and only one of these three conditions:

a) is divisible by 5,

b) da rest 2 to divide by 7,

c) the sum of its digits is divisible by 9.

For example, 37 is nice because the condition b but not the other two, but the 324 is ugly, because it meets the conditions b and c. Similarly, we could say that 41 and 450 are horrible. The first, because it does not meet any of the three conditions, and second, because it is an exaggerated and meets all three.

Do you think your number is nice?