[math-fun] Visible products of touching digits

5420976318, 5630187924, 9071532486, etc. In those numbers K, all products of touching digits are visible in K itself (as a substring). For the first K, for instance, the product 5x4 ("20") is a substring of K, as are 4x2 ("8"), 2x0 ("0"), 0x9 ("0"), 9x7 ("63"), 7x6 ("42"), 6x3 ("18"), 3x1 ("3") and 1x8 ("8"). Will you find all such integers -- or at least the smallest and the biggest ones? K integers MUST be 10-digit long and those ten digits must be different one from another. Hope this is not old hat... Best, and HNY to everyone! É.