Android build error

I can't build my game for Android. I installed Android sdk, Build-Tools and everything (It's not my first time working with Android - so this shouldn't be the issue I hope. But everytime I try to build my game for android out of unity I got this error:

 FormatException: Input string was not in a correct format.
 System.Version+VersionResult.SetFailure (System.Version+ParseFailureKind failure, System.String argument) (at <e1a80661d61443feb3dbdaac88eeb776>:0)
 System.Version.TryParseComponent (System.String component, System.String componentName, System.Version+VersionResult& result, System.Int32& parsedComponent) (at <e1a80661d61443feb3dbdaac88eeb776>:0)
 System.Version.TryParseVersion (System.String version, System.Version+VersionResult& result) (at <e1a80661d61443feb3dbdaac88eeb776>:0)
 System.Version.Parse (System.String input) (at <e1a80661d61443feb3dbdaac88eeb776>:0)
 System.Version..ctor (System.String version) (at <e1a80661d61443feb3dbdaac88eeb776>:0)
 UnityEditor.Android.Utils.ParseVersion (System.String version) (at <41da61d7f28641bd8862fbf18dbc2b26>:0)
 UnityEditor.Android.AndroidComponentProperties.get_PackageRevision () (at <41da61d7f28641bd8862fbf18dbc2b26>:0)
 UnityEditor.Android.AndroidComponentProperties.GetPackageRevision (System.String directory) (at <41da61d7f28641bd8862fbf18dbc2b26>:0)
 UnityEditor.Android.AndroidSDKTools.BuildToolsVersion () (at <41da61d7f28641bd8862fbf18dbc2b26>:0)
 UnityEditor.Android.PostProcessor.Tasks.CheckAndroidSDK+SDKBuildToolsDetector.GetVersion (UnityEditor.Android.AndroidSDKTools sdkTools, UnityEditor.Android.AndroidJavaTools javaTools) (at <41da61d7f28641bd8862fbf18dbc2b26>:0)
 UnityEditor.Android.PostProcessor.Tasks.CheckAndroidSDK+SDKComponentDetector.Detect (UnityEditor.Android.AndroidSDKTools sdkTools, UnityEditor.Android.AndroidJavaTools javaTools, System.Version minVersion, UnityEditor.Android.PostProcessor.ProgressHandler onProgress) (at <41da61d7f28641bd8862fbf18dbc2b26>:0)
 UnityEditor.Android.PostProcessor.Tasks.CheckAndroidSDK.EnsureSDKComponentVersion (UnityEditor.Android.AndroidJavaTools javaTools, System.Version minVersion, UnityEditor.Android.PostProcessor.Tasks.CheckAndroidSDK+SDKComponentDetector detector) (at <41da61d7f28641bd8862fbf18dbc2b26>:0)
 UnityEditor.Android.PostProcessor.Tasks.CheckAndroidSDK.EnsureSDKComponentVersion (UnityEditor.Android.AndroidJavaTools javaTools, System.Int32 minVersion, UnityEditor.Android.PostProcessor.Tasks.CheckAndroidSDK+SDKComponentDetector detector) (at <41da61d7f28641bd8862fbf18dbc2b26>:0)
 UnityEditor.Android.PostProcessor.Tasks.CheckAndroidSDK.Execute (UnityEditor.Android.PostProcessor.PostProcessorContext context) (at <41da61d7f28641bd8862fbf18dbc2b26>:0)
 UnityEditor.Android.PostProcessor.PostProcessRunner.RunAllTasks (UnityEditor.Android.PostProcessor.PostProcessorContext context) (at <41da61d7f28641bd8862fbf18dbc2b26>:0)
 UnityEditor.Android.PostProcessAndroidPlayer.PrepareForBuild (UnityEditor.BuildOptions options, UnityEditor.BuildTarget target) (at <41da61d7f28641bd8862fbf18dbc2b26>:0)
 UnityEditor.Android.AndroidBuildPostprocessor.PrepareForBuild (UnityEditor.BuildOptions options, UnityEditor.BuildTarget target) (at <41da61d7f28641bd8862fbf18dbc2b26>:0)
 UnityEditor.PostprocessBuildPlayer.PrepareForBuild (UnityEditor.BuildOptions options, UnityEditor.BuildTargetGroup targetGroup, UnityEditor.BuildTarget target) (at C:/buildslave/unity/build/Editor/Mono/BuildPipeline/PostprocessBuildPlayer.cs:106)
 UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

MinSDK is API 16 (which I installed of course) and Target SDK is the most recent. I also changed the packagename.

Can anybody help me?