Amazon Kindle Fire HDX has a pixel density of:
323.45

A.K.A. Kindle Fire HDX 7″
Released: 2013

Resolution: 1920×1200 7″ display

Wide UXGA (WUXGA) 1920×1200, 16:10 aspect ratio

Totaling 2.30mp (megapixels) and having a PPI of 323.45

Category: Tablet
Tags: kindle, fire, hdx, display

Amazon Fire HDX

Fire HDX 7 (3rd gen, 2013)
Developer	Amazon.com
Type	Tablet computer
Release date	7″ model October 18, 2013 8.9″ model November 7, 2013 (USA)
Operating system	Fire OS 3, upgradable to Fire OS 5
System-on-chip used	Qualcomm Snapdragon 800
CPU	Quad-core 2.2 GHz ARM Krait 400
Memory	2 GB
Storage	16/32/64 GB
Display	7″ model: 1920 × 1200 px 323 PPI 7 in (18 cm) diagonal 8.9″ model: 2560 × 1600 px 339 PPI 8.9 in (23 cm) diagonal
Graphics	Adreno 330
Sound	Stereo speakers
Input	GPS, accelerometer, gyroscope, light sensor
Camera	Front; 8.9″ model only: 8 MP Rear
Connectivity	Micro-USB 2.0 (type B) 3.5 mm stereo socket Dual-band 802.11 a/b/g/n WiFi 4G LTE Bluetooth 4.0
Online services	Amazon Prime, Amazon Cloud Storage, Amazon Cloud Player, Amazon video, Amazon Silk, Amazon Appstore, Amazon Kindle Store
Dimensions	7″ model: 186×128×9.0 mm (7.3×5.0×0.35 in) 8.9″ model: 231×158×7.8 mm (9.1×6.2×0.31 in)
Mass	7″ model: WiFi 303 g, 4G 311 g 8.9″ model: WiFi 374 g, 4G 384 g
Predecessor	Fire HD
Successor	Fire HD
Website	Amazon Kindle Fire HDX

This righthand infobox courtesy of Wikipedia.