MHS successful candidate
The first digit can be 4, 5, or 6 (3 choices). The remaining 3 digits can be any of the remaining 4 digits (4 choices for the second, 3 for the third, and 2 for the fourth). The number of 4-digit numbers is 3x4x3x2=72.
All 5 digits can be used in any order.
The number of 5-digit numbers is 5! = 120
72+120=192 numbers