int szam = 12345

byte seg_table[] = {
  //pgfedcba
  0b00111111, //0
  0b00000110, //1
  0b01011011, //2
  0b01001111, //3
  0b01100110, //4
  0b01101101, //5
  0b01111101, //6
  0b00000111, //7
  0b01111111, //8
  0b01101111, //9
}

void setup() {
DDRD = 0xFF;
DDRB = 0xFF;
}

void loop() {
  PORTD = seg_table[szam/1000];
  PORTB = 0B11111110;
  PORTB = 0B11111111;
  delay(20);
  PORTD= seg_table[szam%1000/100];
  PORTB = 0B11111101;
  PORTB = 0B11111111;
  delay(20);
  PORTD = seg_table[szam%100/10];
  PORTB = 0B11111011;
  PORTB = 0B11111111;
  delay(20);
  PORTD = seg_table[szam%10];
  PORTB = 0B11110111;
  PORTB = 0B11111111;
  delay(20);
}