It varies from person to person and depending what sort of activities you do but the amount you said sounds way too little for anyone. Depending on what kind of workout I do during the day and how much I used my brain (studying really hard or taking exams makes me need mroe sleep) I need between 7 and 8.5 hours of sleep (9 in extreme cases). You run some serious risks from now getting enough sleep and I ahve gotten sick from that before. It lowers your imune system, puts you at greater risk for injury, hurts your recovery times, and makes you feel tired and lousy all the time.
I have had times when I worked nights and days, two diferent jobs, and didn't sleep hardly at all and that felt terrible. I did not perform well on the job either. Felt sort of like Edward Norton in Fight Club.