function IntToBin(AInt: int64): string;
begin
  result := '';
  while AInt > 0 do
  begin
    result := chr(ord('0') + (AInt and 1)) + result;
    AInt := AInt shr 1;
  end;
end;

function BinToInt(AStr: string): int64;
var
  CurrPos: integer;
begin
  result := 0;
  if Length(AStr) > 64 then
    raise EOverflow.Create('Integer value can have at maximum 63 bit!');
  CurrPos := 1;
  while Length(AStr) >= CurrPos do
  begin
    result := result shl 1;
    case AStr[CurrPos] of
      '0', '1':
        result := result + ord(AStr[CurrPos]) - ord('0');
      else
        raise EConvertError.CreateFmt('Not a valid binary value: %s',
          [AStr]);
    end;
    inc(CurrPos);
  end;
end;

Необходимо подключить модуль SysUtils.