Invariants of finite solvable groups

The review of the results connected with invariants of finite solvable groups is given in this article. These results adjoin to the researches of authors. Section 1 contains the list of used designations and definitions. The data about invariants of solvable groups with given structure of Sylow subgroups are collected in Section 2. The estimations of the invariants depending on indexes of the maximal subgroups are listed in Section 3. The information about nilpotent $\pi$-length of $\pi$-solvable groups are contained in Section 4. Open questions are formulated.