Palindromic Smith Number

Sequence

The sequence of palindromic Smith numbers begins:

$4, 22, 121, 202, 454, 535, 636, 666, 1111, 1881, 3663, 7227, 7447, 9229, 10 \, 201, 17 \, 271, 22 \, 522, 24 \, 142, \ldots$

Examples

$123 \, 455 \, 554 \, 321$ is a Palindromic Smith Number

$123 \, 455 \, 554 \, 321 = 11 \times 41 \times 73 \times 101 \times 137 \times 271$

and:

$1 + 2 + 3 + 4 + 5 + 5 + 5 + 5 + 4 + 3 + 2 + 1 = 40 = 1 + 1 + 4 + 1 + 7 + 3 + 1 + 0 + 1 + 1 + 3 + 7 + 2 + 7 + 1$

Sources

• Feb. 1994: Underwood Dudley: Smith Numbers (Math. Mag. Vol. 67, no. 1: pp. 62 – 65)  www.jstor.org/stable/2690561

• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $12,345,554,321$