The number

## 357686312646216567629137

is a prime number.

If you remove any number of digits from the left side, the resulting number is also prime.

Numbers like this are called left-truncatable primes (they must not contain any zeros). There are exactly 4259 others ( BTW, 4259 is a prime).

There are also exactly 82 right-truncatable primes; the largest is 73939133.

Then there are 15 primes that are both left- and right-truncatable. The largest is 739397.

(For more on truncatable primes click here.)

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