| Manufacture | Nokia | Nokia |
| Model | N91 | E51 |
| Form factor | Other | Block |
| Weight | 156 gram | 100.00 |
| Dimensions (HxWxD) | 113 x 55 x 22 | 114.00 x 46.00 x 12.00 |
| Operating System | Other | Other |
| Networks | 2G - 900/1800/1900
| 2G - 850/900/1800/1900
3G - 2100 |
| HSCSD |  | |
| GPRS |  | |
| EDGE | | |
| UMTS | | |
| HSDPA | | |
| HSPA+ | | |
| WiMAX | | |
| LTE (4G light) | | |
| WLAN / Wi-Fi | | |
| Wi-Fi Hotspot | | |
| Wi-Fi Direct | | |
| SMS | | |
| MMS | | |
| Email | | |
| HDMI out | | |
| USB port | | |
| MHL | | |
| Bluetooth | | |
| Bluetooth version | NA | NA |
| DLNA | | |
| GPS | | |
| Glonass | | |
| ANT+ | | |
| IrDA | | |
| NFC | | |
| 3.5 mm audio connector | | |
| Camera | | |
| Camera resolution | 2 Megapixels (1600x1200) | 2 Megapixels, 4x digital zoom |
| Image Stabilization | | |
| BSI sensor | | |
| Camera Flash/Light | | |
| Flash type | NA | NA |
| Video recording | | |
| Video capture resolution | NA | NA |
| Second Camera | NA | NA |
| Display size | 2.1 inches | 2.00 |
| Touchscreen | | |
| Colour display | | |
| Number of colours | 262144 | 16000000 |
| Display width | 176 | 240 |
| Display height | 208 | 320 |
| PPI | 129.75 | 200.00 |
| Second Display | NA | NA |
| CPU | NA | NA |
| GPU | NA | NA |
| Memory | 4 GB internal, 30 MB for contact storage | 130 MB. Expandable up to 4 GB with microSD card |
| Micro SIM | | |
| Dual SIM | | |
| MP3 | | |
| Ringtones / Music file format | Polyphonic, True tones | MP3, MPEG-4, AAC, eAAC+, WMA, AMR-NB, an |
| Java | | |
| Games | Java | NA |
| FM Radio | | |
| Battery | Li-Ion 900 mAh | 1070 mAh |
| Standby time (h) | 190 | 312 |
| Talktime (m) | 240 | 264 |
| Wireless Charging | | |
| Browser | 2.0 XHTML | XHTML |
| Calendar | | |
| Voicedialing | | |
| IP Code | NA | NA |
| Predictive text | | |
| RSS reader | | |
| Voicememo | | |
| PC Synchronization | | |
| SyncML | | |
| Website | Website | Website |
