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Smith number (another Prime Pages' Glossary entries) |
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Glossary:
Prime Pages:
Top 5000:
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In 1982, when Albert Wilansky called his brother-in-law, he
noticed that the phone number was composite and that the
sum of the digits in the phone number equals the sum of the digits in its prime factors.
4937775 = 3.5.5.65837Composite numbers with this property are now called Smith numbers after the brother-in-law Wilansky was calling. Trivially, all prime numbers have this property, so they are excluded. The Smith numbers less than 1000 are: 4, 22, 27, 58, 85, 94, 121, 166, 202, 265, 274, 319, 346, 355, 378, 382, 391, 438, 454, 483, 517, 526, 535, 562, 576, 588, 627, 634, 636, 645, 648, 654, 663, 666, 690, 706, 728, 729, 762, 778, 825, 852, 861, 895, 913, 915, 922, 958, and 985. In 1987, Wayne McDaniel showed that are infinitely many Smith numbers by constructing a sequence of them. If Rn is a repunit prime, then 1540.Rn is a Smith number (with digital sum 18+n). Note that 1540 is not the only possible mutiplier here, others include: 1540, 1720, 2170, 2440, 5590, 6040, 7930, 8344, 8470, 8920, 23590, 24490, 25228, 29080, 31528, 31780, 33544, 34390, 35380, 39970, 40870, 42490, 42598, 43480, 44380, 45955, 46270, 46810, 46990, 47908, 48790, and 49960.
See Also: EconomicalNumber Related pages (outside of this work)
References:
Chris K. Caldwell © 1999-2013 (all rights reserved)
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