char buffer[20];
int amount, count, N, Delitel, AmountPrimeNumber;
int ArrayInt[count]; // здесь count
//...
{
char buffer [20];
int count;
int ArrayInt[amount]; // здесь amount
for (count = 0; count < amount; count++)
{
printf ("ArrayInt[%d] = ", count);
fgets( buffer, 18, stdin );
ArrayInt[count] = atoi(buffer);
}
}