Displaying Prime Numbers

//Global Variables
int ledPin[]={9,2,3,4,5,6,7,8};
char finalStr[8];
bool prime;

void setup()
{
  Serial.begin(9600);
  for(int c=0;c<8;c++)pinMode(ledPin[c],OUTPUT); //Sets all pins to output
}

int primeDisplay(int num)
{
  uint8_t bitsCount=sizeof(num)*8; //Converts integer to binary string
  char str[bitsCount+1];
  uint8_t i=0;
  while(bitsCount--)str[i++]=bitRead(num,bitsCount)+'0';
  str[i]='\0';
  char finalStr[8];
  for(int c=0;c<8;c++)finalStr[c]=str[c+7];
  finalStr[0]=str[8];
  finalStr[1]=str[9];
  finalStr[2]=str[10];
  finalStr[3]=str[11];
  finalStr[4]=str[12];
  finalStr[5]=str[13];
  finalStr[6]=str[14];
  finalStr[7]=str[15];
  for(int c=0;c<8;c++)digitalWrite(ledPin[c],LOW); //Resets pins
  for(int c=0;c<8;c++)if(finalStr[c]=='1')digitalWrite(ledPin[c],HIGH); //Lights up appropriate pins
}

void loop()
{
  for(int c=2;c<255;c++) //Determines prime numbers
  {
    prime=true;
    for(int x=2;x*x<=c;x++)
    {
      if (c%x==0)
      {
        prime=false;
        break;
      }
    }
    if(prime==true)
    {
      Serial.println(c); //Shows prime number as an int to the serial monitor
      primeDisplay(c); //Displays prime number in binary with LEDs
      delay(1000);
    }
  }
}