Decending order in SQlite android not correct

I have problem when descending order in sqlite, i have record in field 'kd_people' like this :

    P1
    P2
    P3
    P4
    P5
    P10

When create query "select kd_people from people order by kd_people desc", the result like :

    P1
    P10
    P2
    P3
    P4
    P5

but i want result like this:

    P10
    P5
    P4
    P3
    P2
    P1

so how the correct query ? thanks, sorry for my english