What resolution do I beed to export a video I want to view on my phone?

[doubletsuki]

I already changed the comp settings to my phone screen's resolution but when I export my video and transfer it to my phone, the video is extremely small and loss of quality is huge when I zoom in. I want to know how I can export my video so it fits exactly on my phone screen's resolution. (The resolution is 1125x2436, portrait mode.) When in AE, the clips fit inside the comp perfectly but when exported, it's a mess. Any tips? 

I attached a screenshot from my phone of how the clip looks like when I try to view it. 

[Byron Cortez]

Show us how are you setting the Output. 

[Rick Gerard]

Just use 1080 X 1920, Standard HD Vertical.

Video cannot be an odd number of pixels in either direction and if you use nonstandard frame sizes the compression will raise hell with the images. Let your phone resize the video and you'll have to live with the black border or let your phone crop the video as it does with all the other videos you play on your phone.