123457
This number is a prime.
When you remove the penultimate (next to the last) digit of 123457 you will end up with yet another prime. Repeat the process for four more primes. [Brod]
The smallest prime formed from the first six imperfect numbers in order. [Beedassy]
The sum of the repunit number 111111 and all truncations of itself plus one is prime. [Loungrides]
The smallest prime whose 2nd, 3rd, 4th, and 5th digits are
2, 3, 4, and 5 respectively (OEIS A371845). Coincidentally, 6
is absent from the number. This is also the smallest
6-digit prime with strictly increasing digits (OEIS
A071362). If its
digits are taken as (a, b, c, d, e, f) = (1, 2, 3, 4, 5,
7), then except the initial term a!² = 1, all partial sums
of squared factorials (a!² + b!², a!² + b!² + c!², …) are
prime. [Ahmed]