A mathematics professor complained to the policeman that a student had almost run him down as he attempted to cross the street.

arithmetic/digits/license.plate New, unsolved

New entry, edited from material collected for the archive and not yet in a released version.

Problem

A mathematics professor complained to the policeman that a student had
almost run him down as he attempted to cross the street.  "Did you get
his number?" the policeman asked.  "Well, not exactly," the professor
said.  "But I do remember noticing that if it were multiplied by itself
and then doubled, the square root of the product was the original
number with the digits reversed."  What was the number?

Show solution

No solution was found in the collected postings.

[ Editor: the puzzle was posted by Brian Reese <brianr@phred.UUCP> as a
"bone" at the end of a question about divisibility tests. ]