Smith

A Smith number is a composite number for which the sum of its digits equals the sum of the digits of its prime factors (counting multiplicity). For example, 22 = 2 × 11 and 2 + 2 = 2 + 1 + 1.

Key features

• Named after Harold Smith; all primes are trivially excluded (no composite factorization).
• Repunit primes are not Smith numbers.

Examples:

4, 22, 27, 58, 85, 94

Further reading

• Smith on Wikipedia
• Smith on OEIS