foreign key is not working when I migrate

Foreign key is not working.

This is my migration file

Schema::create('course_prospect', function (Blueprint $table) {
      $table->bigIncrements('id');

      $table->integer('prospect_id')->length(11)->unsigned();
      $table->foreign('prospect_id')->references('id')->on('prospect');

      $table->integer('course_id')->length(11)->unsigned();
      $table->foreign('course_id')->references('course_id')->on('course');

      $table->timestamps();
    });

I'm getting this error

 Illuminate\Database\QueryException  : SQLSTATE[HY000]: General error: 
1005 Can't create table `customerinquirydb`.`#sql-104c_e9` (errno: 150 
"Foreign key constraint is incorrectly formed") (SQL: alter table 
`course_prospect` add constraint `course_prospect_prospect_id_foreign` 
foreign key (`prospect_id`) references `prospect` (`id`))

via Chebli Mohamed