MathDB

Very prime number

Source: Azerbaijan NMO 2016. Senior P3

July 27, 2023

number theoryprime numbers

Problem Statement

Let's call any natural number "very prime" if any number of consecutive digits (in particular, a digit or number itself) is a prime number. For example,

23

and

37

are "very prime" numbers, but

237

and

357

are not. Find the largest "prime" number (with justification!).

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