# A Math trick with the number 246,913,578

Kindly see this trick question and help me know as to how it works:

The answer is always 123456789, how does it works? Can someone help me out here?

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I don't think there's any trick here. It's just a coincidence. –  tomasz Jun 21 '12 at 13:33
It's not entirely coincidence: 246,913,578 = 2·123,456,789. So of course that's what you get if you multiply by 5 or divide by 2. But I find it surprising that that's what you get if you multiply by 7, and I think there's something else at work here. –  MJD Jun 21 '12 at 13:39
It's also suspicious that none of those numbers are divisible by 3. –  rschwieb Jun 21 '12 at 13:54
Have you seen When multiplication mixes up digits ? –  Peter Phipps Jun 21 '12 at 14:11
What bothers me slightly is that some interesting numbers to multiply by that work are missing; why was the prime 17 (and 409 and 439) skipped but not 31? All the numbers less than 1000 which work are 1,2,4,5,7,8,10,11,13,16,17,20,22,25,26,31,35,40,‌​50,55,65,70,80,85,100,110,115,125,130,155,160,170,175,200,205,209,215,220‌​,250,260,265,305,310,350,355,400,409,418,425,427,439,500,550,650,700,800,818,850,‌​875. As an aside, the next closest pandigital number starting with 2 is 213497865, with a mere 25 multipliers below 1000. –  Mark S. Jan 11 '13 at 18:55