Left-Truncatable Prime/Examples/357,686,312,646,216,567,629,137

Theorem

The largest left-truncatable prime is $357 \, 686 \, 312 \, 646 \, 216 \, 567 \, 629 \, 137$.


Proof

First it is demonstrated that $357 \, 686 \, 312 \, 646 \, 216 \, 567 \, 629 \, 137$ is indeed a left-truncatable prime:

\(\ds 357 \, 686 \, 312 \, 646 \, 216 \, 567 \, 629 \, 137\) \(\) \(\ds \) is prime
\(\ds 57 \, 686 \, 312 \, 646 \, 216 \, 567 \, 629 \, 137\) \(\) \(\ds \) is prime
\(\ds 7 \, 686 \, 312 \, 646 \, 216 \, 567 \, 629 \, 137\) \(\) \(\ds \) is prime
\(\ds 686 \, 312 \, 646 \, 216 \, 567 \, 629 \, 137\) \(\) \(\ds \) is prime
\(\ds 86 \, 312 \, 646 \, 216 \, 567 \, 629 \, 137\) \(\) \(\ds \) is prime
\(\ds 6 \, 312 \, 646 \, 216 \, 567 \, 629 \, 137\) \(\) \(\ds \) is prime
\(\ds 312 \, 646 \, 216 \, 567 \, 629 \, 137\) \(\) \(\ds \) is prime
\(\ds 12 \, 646 \, 216 \, 567 \, 629 \, 137\) \(\) \(\ds \) is prime
\(\ds 2 \, 646 \, 216 \, 567 \, 629 \, 137\) \(\) \(\ds \) is prime
\(\ds 646 \, 216 \, 567 \, 629 \, 137\) \(\) \(\ds \) is prime
\(\ds 46 \, 216 \, 567 \, 629 \, 137\) \(\) \(\ds \) is prime
\(\ds 6 \, 216 \, 567 \, 629 \, 137\) \(\) \(\ds \) is prime
\(\ds 216 \, 567 \, 629 \, 137\) \(\) \(\ds \) is prime
\(\ds 16 \, 567 \, 629 \, 137\) \(\) \(\ds \) is prime
\(\ds 6 \, 567 \, 629 \, 137\) \(\) \(\ds \) is prime
\(\ds 567 \, 629 \, 137\) \(\) \(\ds \) is prime
\(\ds 67 \, 629 \, 137\) \(\) \(\ds \) is the $3 \, 986 \, 726$th prime
\(\ds 7 \, 629 \, 137\) \(\) \(\ds \) is the $516 \, 434$th prime
\(\ds 629 \, 137\) \(\) \(\ds \) is the $51 \, 275$th prime
\(\ds 29 \, 137\) \(\) \(\ds \) is the $3167$th prime
\(\ds 9 \, 137\) \(\) \(\ds \) is the $1133$rd prime
\(\ds 137\) \(\) \(\ds \) is the $33$rd prime
\(\ds 37\) \(\) \(\ds \) is the $12$th prime
\(\ds 7\) \(\) \(\ds \) is the $4$th prime


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Sources

  • 1977: I.O. Angell and H.J. Godwin: On Truncatable Primes (Math. Comp. Vol. 31: pp. 265 – 267)  www.jstor.org/stable/2005797
  • 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $357,686,312,646,216,567,629,137$
  • 1987: C. Caldwell: Truncatable primes (J. Recr. Math. Vol. 19, no. 1: pp. 30 – 33)
  • 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $357,686,312,646,216,567,629,137$