In this proposition, the dividend is 14N, the divisor is 10, and the remainder is 6. Therefore, no matter what integer the quotient is, if you multiply it by 10 and add 6, there will be a unit number of 6, so 14N is a unit number of 6;

In the product of dividend 14 and n, the unit number 4 of 14 will only appear 6 when multiplied by 4 or 9, that is, dividend 14N is divided by divisor 10, and the rest is 6. Therefore, the number of digits of n should be 4 or 9.