unit Unit1;

interface

uses

  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,

  Vcl.Controls, Vcl.Forms, Vcl.Dialogs;

type

  TForm1 = class(TForm)

    procedure FormCreate(Sender: TObject);

  private

    { Private declarations }

  public

    { Public declarations }

  end;

var

  Form1: TForm1;

implementation

{$R *.dfm}

uses System.Character;

function getNumberFromStr(strIn: string): string;

var

  i: integer;

  tempStr: string;

begin

  tempStr := '';

  if Length(strIn) = 0 then

  begin

    Result := '';

    exit;

  end;

  for i := 1 to strIn.Length do

  begin

    if IsNumber(strIn[i]) then    //isNumber--System.Character

    begin

      tempStr := tempStr + strIn[i];

    end;

  end;

  Result := tempStr;

end;

procedure TForm1.FormCreate(Sender: TObject);

begin

   caption:=getNumberFromStr('abc123456 789789');

end;

end.