BigNumber.h Arduino how to parse a number larger then 10 digits

Question

i have made a simple bit of code to test a number to see if it is a prime number or not but while feeding it large prime numbers to test the speed of the program on the arduino it whould only take a number at length 9-/under-digits i tested my read function and it returns the entire number but the 'BigNumber' wont parse it insted it just says its 0

code:

void Speed(String num)
{
    Serial.println("NUM="+num);
    BigNumber NUM = num.c_str();//this is where it fails
    BigNumber Curr = "1";//start 2 / 'curr++' start of loop
    num = "";
    ... the testing of prime numbers here

the code stops the arduino if i put a 10 digit number in, the output is so

<|S 1234567891
>|NUM=1234567891

and if i put a number with 9 digits it outputs as expected

<S 123456789
>|NUM=123456789
>|123456789 is not a prime number 
>|because ist a factor of 3

i have tryed seeing if anyone has had the same problem as me but i cant find it anywhere.

im use an arduino-uno

EDIT: after doing some more testing it now doesnt set the number insted of crashing after testing 'S 1111111111' (10 digits) its output is normal:

<|S 1111111111
>|NUM=1111111111
>|1111111111 is not a prime number 
>|because ist a factor of 11

but if i put in 11 digits it parses as 0 ??

<|S 11111111111
>|NUM=11111111111
>|0 cant be a prime number because it doesn't end in 1,3,7,9

bty: i forgot to mention that 'S number_here' S specifys the mothod of finding the result i also have D=DataCrunch it checks all the numbers and L=List witch creates a list of found Prime numbers like a prime number search, and thay work fine exept that DataCrunch (D) has the same problem with parsing the number given.

EDIT2: this is proof that BigNumber can hold such a large number https://forum.arduino.cc/index.php?topic=85692.0 in the first post.

Answer 1

so as it turns out after some extensiv research that BigNumber is not fit for very large numbers but another part of the 'BigNumber.h' lib does its bc_num.

bc_num x;
bc_str2num(&x, "9898989898", 10);
String c = "Controll=";
c+=bc_num2str(x);
Serial.println(c);

output

Controll=9898989898

but as you can see this takes a bit more programming to get implamented and so im going to go off and start now bye.