void setup() {

  Serial.begin(115200);

  uint8_t             a = -1; Serial.println("uint8_t:");
                              Serial.println(a);

  unsigned int        b = -1; Serial.println("\nunsigned int:");
                              Serial.println(b);
  uint16_t            c = -1; Serial.println("uint16_t:");
                              Serial.println(c);

  uint32_t            d = -1; Serial.println("\nuint32_t:");
                              Serial.println(d);
  unsigned long       e = -1; Serial.println("unsigned long:");
                              Serial.println(e);

  uint64_t            f = -1;
  unsigned long long  g = -1;

  uint64_t            billion =  1000000;
                      billion *= 1000000; // 1 metric-billion

  Serial.println("\nuint64_t:");
  Serial.print(uint32_t(f / billion));Serial.println(" * million^2");
  Serial.println("unsigned long long:");
  Serial.print(uint32_t(g / billion));Serial.println(" * million^2");
}

void loop() {}