Google Research

Repeatedly Appending Any Digit to Generate Composite Numbers

  • John Grantham
  • Witold Jarnicki
  • Jon Rickert
  • Stan Wagon
The American Mathematical Monthly (2012) (to appear)


We investigate the problem of nding integers k such that ap- pending any number of copies of the base-ten digit d to k yields a composite number. In particular, we prove that there exist in nitely many integers co- prime to all digits such that repeatedly appending any digit yields a composite number.

Learn more about how we do research

We maintain a portfolio of research projects, providing individuals and teams the freedom to emphasize specific types of work