Question about the 401k retirement?

i am wondering about this as this is important to me to know in the future. I'm going to college as a nurse and if i land a job as a lvn and get 401k retirement when do nurses retire? do they retire at the age of 65 is there such thing as 65 year old nurses? does the 401k retirement counts as whole? or is it little by month? what about ssi retirement plan too? i can have that? i don't know if i want to retire as a nurse though i can't really go to school to learn 2 trades as 1 is enough. i'm hoping to land a job in the front desk if i get to old for it.