123456789
it has so many sides it looks like a circle.
I am delighted to say that there are actually nine ways! 12 x 483 = 5796 42 x 138 = 5796 18 x 297 = 5346 27 x 198 = 5346 28 x 157 = 4396 39 x 186 = 7254 48 x 159 = 7632 4 x 1738 = 6952 4 x 1963 = 7852 I wrote some javascript (don't know any other programming codes!) to come up with the first seven. It was little more than a search through the various permutations, with only a few shortcuts. (It would be interesting if anybody could think of a neater way of finding the solutions.) I overlooked the last two - Henry Ernest Duden takes sole credit for them. The list is exhaustive - there are no other solutions.
1.524157875019052e+16
123456789 + 123456789 = 246913578
15,241,578,750,190,521
you get cheese
543234567890-123456789 = 543111111101
1
324536
123456789 + 36853168 = 160309957
123456789 +987654321 =1111111110
123456789-987654321 = -864197532
123456789 X 123456789 is1.52415788 × 1016
100000000-123456789 = -23456789