openrtb-core/src/main/java/com/google/openrtb/json/OpenRtbJsonUtils.java
public static void writeLong(long data, JsonGenerator gen) throws IOException {
    if (data > MAX_JSON_INT || data < -MAX_JSON_INT) {
      gen.writeString(Long.toString(data));
    } else {
      gen.writeNumber(data);
    }
  }
public static void writeLong(long data, JsonGenerator gen) throws IOException {
    if (data > MAX_JSON_INT || data < -MAX_JSON_INT) {
      gen.writeString(Long.toString(data));
    } else {
      gen.writeNumber(data);
    }
  }
Writes a long, using quotes only if it's too big (over 53-bit mantissa).