Why can't 520 be divided by 3?

① 520 = 2x5xx13, that is, the prime factor of 520 does not contain 3, so it is not a multiple of 3, so it cannot be divisible;

②520/3 is simplest fraction, and simplest fraction whose denominator only contains prime factors 2 and 5 can be converted into a finite decimal (that is, divisible), otherwise it cannot be converted into a finite decimal. According to the relationship between fraction and division, if a number is divisible by 3, as long as the number is not a multiple of 3, its quotient must be an infinite cycle decimal.