Oh, dude, like, the concept of numbers has been around for ages, you know? But if you're talking about the specific sequence 123456789, I mean, that's just a natural progression of numbers, man. It's like asking who invented counting - it's been around forever, like before the dinosaurs or something.
123456789 + 123456789 = 246913578
the answer is 15241578750190521
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