2357
This number is a prime.
Just showing those entries submitted by 'De Geest': (Click here to show all)
Inserting nineteen zeros between the four prime digits of 2357 makes another prime of prime length sixtyone. Note that 23 + 57 = 19 + 61 and also 19 + 4 = 23 as 57 + 4 = 61. [De Geest]
The prime digits united by unities is prime (2131517). [De Geest]
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