A066307 Nonprimes whose sum of digits is equal to its product of digits.

1, 4, 6, 8, 9, 22, 123, 132, 213, 231, 312, 321, 1124, 1142, 1214, 1241, 1412, 1421, 2114, 4112, 4121, 11125, 11133, 11152, 11215, 11222, 11313, 11331, 11512, 11521, 12115, 12122, 12151, 12212, 12221, 13113, 13131, 13311, 15112, 15211, 21115

Offset: 1

Author

Labos Elemer, Dec 13 2001

Keywords

• base
• nonn

Examples

			321 = 3*107, 3 + 2 + 1 = 6 = 3*2*1.
		

Links

• Chai Wah Wu, Table of n, a(n) for n = 1..10000 (n = 1..516 from Harry J. Smith)

Crossrefs

Composites and 1 from A034710.

Cf. A034710, A066306.

Programs

Mathematica

sdpdQ[n_]:=Module[{idn=IntegerDigits[n]},Total[idn]==Times@@idn]; Module[ {upto=25000, cs},cs=Complement[Range[upto],Prime[Range[PrimePi[upto]]]];Select[cs,sdpdQ]] (* Harvey P. Dale, Oct 14 2014 *)

PARI

isok(k) = {if(isprime(k), 0, my(d=digits(k)); vecprod(d) == vecsum(d))} \\ Harry J. Smith, Feb 09 2010