Smith number

Smith number
Named afterHarold Smith (brother-in-law of Albert Wilansky)
Author of publicationAlbert Wilansky
Total no. of termsinfinity
First terms4, 22, 27, 58, 85, 94, 121
OEIS indexA006753

In number theory, a Smith number is a composite number for which, in a given number base, the sum of its digits is equal to the sum of the digits in its prime factorization in the same base. In the case of numbers that are not square-free, the factorization is written without exponents, writing the repeated factor as many times as needed.

Smith numbers were named by Albert Wilansky of Lehigh University, as he noticed the property in the phone number (493-7775) of his brother-in-law Harold Smith:

4937775 = 3 · 5 · 5 · 65837

while

4 + 9 + 3 + 7 + 7 + 7 + 5 = 3 + 5 + 5 + (6 + 5 + 8 + 3 + 7)

in base 10.[1]

  1. ^ Sándor & Crstici (2004) p.383