Explanation :
First we will add the digits of every number i.e.
12439 : 1 + 2 + 3 + 4 + 9 = 19
23549 : 2 + 3 + 5 + 4 + 9 = 23
34659 : 3 + 4 + 6 + 5 + 9 = 27
45769 : 4 + 5 + 7 + 6 + 9 = 31
As we can see that in every case the sum of digits of number is a prime number except in case of 34659.
Hence, 34659 is wrong number in the given series.