## Solution to: Prime numbers with equal digits

**by Christoph Lohe**

In the decimal number system, the first prime number candidates with equal digits are:

** [2] = 11 is a prime number**

[3] = 111 = 3 x 37

[5] = 11111 = 41 x 271

[7] = 1111111 = 239 x 4649

[11] = 11111111111 = 21649 x 513239

[13] = 1111111111111 = 53 x 79 x 265371653

[17] = 11111111111111111 = 2071723 x 5363222357

**[19] = 1111111111111111111 is a prime number**

An open question remains whether there is a largest prime number with equal "1" digits - I don't know the answer. If you find a prime number beyond [19], or if you know about a free prime test program or an online prime test link for numbers with more than 20 digits then please let me know.