# 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?

• 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