9

• 12345679 x 9 = 111111111
  12345679 x 18 = 222222222
  12345679 x 27 = 333333333
  12345679 x 36 = 444444444
  12345679 x 45 = 555555555
  12345679 x 54 = 666666666
  12345679 x 63 = 777777777
  12345679 x 72 = 888888888
  12345679 x 81 = 999999999
  12345679 x 999 999 999 = 12345678987654321