Explain why all 6-digit freholl numbers are composite

Fredholl numbers are numbers, which have 2 different digits, equal number of each one, and zero cannot be the first digit.

6-digit fredholl numbers are all composite because, all of them can be divided by 3.

Let's prove it:

Number can be divided by 3, when sum of it's digits can be divided by 3.

6-digit fredholl number must consist of three digits A, and three digits B.

So a sum of their digits is 3A+3B

3A+3B=3 (A+B) so this number is divisible by 3,

Therefore any 6-digit fredholl number is divisible by 3.