This is false.
If Banana corresponds to the code 458124 you would have few possibilities of combination for the letters of BANANA: B=4; A= 5-1-4; N=8-2.
Now if BANANA becomes ANANAB does not matter the combinations of ANANA the last letter which is B should only be the number 4, so the code would have to be 4 in the last letter on the right side. So the code 421458 is not the right one.
