Sorry to hear you lost a friend. Unfortunately denial is the first stage of grieving. Some of us go through the stages faster then others. Just find other mutual friends to talk to and share stories right now. The reality will hit you eventually.
Time. If you want my advice, the only thing to do is give it time. Time heals many wounds, & during that time, look back on the great times you had with your friend. Their will be tears in the process, & some will be for sadness, but let the others be tears of joy, as you reminisce on your friends life. Also, I'm very sorry to hear of your friends death, I will be praying for you