A157676 Numbers n such that n + (product of digits of n) is prime.

1, 21, 23, 27, 29, 61, 67, 81, 83, 101, 103, 107, 109, 161, 163, 169, 233, 239, 253, 259, 283, 289, 293, 299, 307, 329, 341, 343, 347, 349, 361, 401, 409, 431, 437, 439, 441, 443, 449, 471, 473, 477, 493, 499, 503, 509, 529, 563, 569, 601, 607, 611, 613, 617

Offset: 1

Author

Kyle D. Balliet, Mar 04 2009

Keywords

• nonn
• base

Examples

			a(21) = 21 + (2)(1) = 23 (prime). a(67) = 67 + (6)(7) = 109 (prime). a(169) = 169 + (1)(6)(9) = 223 (prime).
		

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A157677, A092518.

Programs

Mathematica

fQ[n_] := PrimeQ[n + Times @@ IntegerDigits@n]; Select[ Range@1000, fQ@# &] (* Robert G. Wilson v, May 04 2009 *)

PARI

dprod(n)=n=digits(n);prod(i=1,#n,n[i])
is(n)=isprime(dprod(n)+n) \\ Charles R Greathouse IV, Dec 27 2013

Formula

a(n) ~ n log n. - Charles R Greathouse IV, Dec 27 2013

Extensions

More terms from Robert G. Wilson v, May 04 2009