We begin with a brute force search for permutable primes less than 10^6. We only list the permutable primes whose digits are in ascending order. The one-digit primes are omitted. 11 13 17 37 79 113 199 337 We will prove that no other permutable primes exist, except for repunits. The proof uses a lemma: If N and m are integers greater than 1 such that the digit permutations of N cover all congruence classes modulo m, then no permutable prime can contain all of the digits of N (as a multiset). By choosing a finite number of pairs (N,m) we can rule out all numbers having six or more digits, except for repunits. Case 1: N has four distinct digits (1,3,7,9). We use m = 7. 1379 = 0 (mod 7) 1793 = 1 (mod 7) 3719 = 2 (mod 7) 1739 = 3 (mod 7) 1397 = 4 (mod 7) 1937 = 5 (mod 7) 1973 = 6 (mod 7) Case 2: N has three distinct digits. Case 2A: N contains aabbc. 13713 = 0 (mod 7) 11733 = 1 (mod 7) 17313 = 2 (mod 7) 13317 = 3 (mod 7) 11337 = 4 (mod 7) 11373 = 5 (mod 7) 13173 = 6 (mod 7) 13139 = 0 (mod 7) 13931 = 1 (mod 7) 19133 = 2 (mod 7) 31139 = 3 (mod 7) 11393 = 4 (mod 7) 11933 = 5 (mod 7) 11339 = 6 (mod 7) 17731 = 0 (mod 7) 17137 = 1 (mod 7) 11377 = 2 (mod 7) 17713 = 3 (mod 7) 17371 = 4 (mod 7) 11737 = 5 (mod 7) 11773 = 6 (mod 7) 11977 = 0 (mod 7) 17179 = 1 (mod 7) 11797 = 2 (mod 7) 19771 = 3 (mod 7) 17791 = 4 (mod 7) 11779 = 5 (mod 7) 71791 = 6 (mod 7) 91931 = 0 (mod 7) 19139 = 1 (mod 7) 11993 = 2 (mod 7) 11399 = 3 (mod 7) 11939 = 4 (mod 7) 19913 = 5 (mod 7) 19193 = 6 (mod 7) 19971 = 0 (mod 7) 17991 = 1 (mod 7) 11979 = 2 (mod 7) 19197 = 3 (mod 7) 11799 = 4 (mod 7) 91971 = 5 (mod 7) 11997 = 6 (mod 7) 37317 = 0 (mod 7) 37731 = 1 (mod 7) 37137 = 2 (mod 7) 33771 = 3 (mod 7) 33177 = 4 (mod 7) 33717 = 5 (mod 7) 31737 = 6 (mod 7) 37793 = 0 (mod 7) 33797 = 1 (mod 7) 37739 = 2 (mod 7) 37397 = 3 (mod 7) 33779 = 4 (mod 7) 37973 = 5 (mod 7) 33977 = 6 (mod 7) 39319 = 0 (mod 7) 93913 = 1 (mod 7) 39391 = 2 (mod 7) 39931 = 3 (mod 7) 33919 = 4 (mod 7) 33199 = 5 (mod 7) 33991 = 6 (mod 7) 39739 = 0 (mod 7) 33979 = 1 (mod 7) 39937 = 2 (mod 7) 33799 = 3 (mod 7) 39379 = 4 (mod 7) 33997 = 5 (mod 7) 37939 = 6 (mod 7) 71799 = 0 (mod 7) 97791 = 1 (mod 7) 77919 = 2 (mod 7) 77199 = 3 (mod 7) 77991 = 4 (mod 7) 79791 = 5 (mod 7) 79197 = 6 (mod 7) 77399 = 0 (mod 7) 77939 = 1 (mod 7) 79739 = 2 (mod 7) 79397 = 3 (mod 7) 79937 = 4 (mod 7) 79973 = 5 (mod 7) 77993 = 6 (mod 7) Case 2B: N contains aaaaabc. 1111173 = 0 (mod 7) 1111713 = 1 (mod 7) 1111371 = 2 (mod 7) 1113171 = 3 (mod 7) 1111317 = 4 (mod 7) 1111731 = 5 (mod 7) 1111137 = 6 (mod 7) 1113119 = 0 (mod 7) 1111139 = 1 (mod 7) 1111931 = 2 (mod 7) 1131119 = 3 (mod 7) 1119311 = 4 (mod 7) 1111913 = 5 (mod 7) 1111193 = 6 (mod 7) 1111719 = 0 (mod 7) 7111119 = 1 (mod 7) 1111791 = 2 (mod 7) 1111197 = 3 (mod 7) 1117911 = 4 (mod 7) 1117191 = 5 (mod 7) 1111179 = 6 (mod 7) 3337313 = 0 (mod 7) 3333317 = 1 (mod 7) 3333731 = 2 (mod 7) 3333137 = 3 (mod 7) 3333173 = 4 (mod 7) 3333713 = 5 (mod 7) 3333371 = 6 (mod 7) 3339133 = 0 (mod 7) 3313339 = 1 (mod 7) 3333913 = 2 (mod 7) 3333319 = 3 (mod 7) 3331339 = 4 (mod 7) 3333391 = 5 (mod 7) 3333931 = 6 (mod 7) 3333379 = 0 (mod 7) 3333793 = 1 (mod 7) 3339373 = 2 (mod 7) 3333739 = 3 (mod 7) 3333397 = 4 (mod 7) 3333937 = 5 (mod 7) 3333973 = 6 (mod 7) 7777371 = 0 (mod 7) 7771737 = 1 (mod 7) 7777317 = 2 (mod 7) 7777731 = 3 (mod 7) 7777137 = 4 (mod 7) 7777173 = 5 (mod 7) 7777713 = 6 (mod 7) 7777791 = 0 (mod 7) 7777197 = 1 (mod 7) 7719777 = 2 (mod 7) 7771977 = 3 (mod 7) 7777179 = 4 (mod 7) 7777719 = 5 (mod 7) 7779771 = 6 (mod 7) 7777973 = 0 (mod 7) 7777379 = 1 (mod 7) 7777793 = 2 (mod 7) 7773797 = 3 (mod 7) 7777739 = 4 (mod 7) 7777397 = 5 (mod 7) 7777937 = 6 (mod 7) 9999913 = 0 (mod 7) 9999193 = 1 (mod 7) 1999993 = 2 (mod 7) 9999139 = 3 (mod 7) 9999931 = 4 (mod 7) 9991399 = 5 (mod 7) 9991939 = 6 (mod 7) 9917999 = 0 (mod 7) 9999179 = 1 (mod 7) 9999971 = 2 (mod 7) 9997991 = 3 (mod 7) 9999917 = 4 (mod 7) 9999197 = 5 (mod 7) 9991799 = 6 (mod 7) 9997939 = 0 (mod 7) 9999739 = 1 (mod 7) 9999397 = 2 (mod 7) 9999937 = 3 (mod 7) 9999973 = 4 (mod 7) 9999379 = 5 (mod 7) 9999793 = 6 (mod 7) Case 3: N has two distinct digits. Case 3A: N contains aaabb. 31311 = 0 (mod 7) 11313 = 1 (mod 7) 13113 = 2 (mod 7) 11133 = 3 (mod 7) 13311 = 4 (mod 7) 11331 = 5 (mod 7) 13131 = 6 (mod 7) 17171 = 0 (mod 7) 17711 = 1 (mod 7) 17117 = 2 (mod 7) 71711 = 3 (mod 7) 11771 = 4 (mod 7) 11177 = 5 (mod 7) 11717 = 6 (mod 7) 11991 = 0 (mod 7) 91911 = 1 (mod 7) 19119 = 2 (mod 7) 19911 = 3 (mod 7) 19191 = 4 (mod 7) 11919 = 5 (mod 7) 11199 = 6 (mod 7) 33131 = 0 (mod 7) 13133 = 1 (mod 7) 31313 = 2 (mod 7) 33113 = 3 (mod 7) 31133 = 4 (mod 7) 33311 = 5 (mod 7) 31331 = 6 (mod 7) 37373 = 0 (mod 7) 33377 = 1 (mod 7) 73733 = 2 (mod 7) 37733 = 3 (mod 7) 33737 = 4 (mod 7) 33773 = 5 (mod 7) 37337 = 6 (mod 7) 93933 = 0 (mod 7) 33993 = 1 (mod 7) 33399 = 2 (mod 7) 33939 = 3 (mod 7) 39393 = 4 (mod 7) 39933 = 5 (mod 7) 39339 = 6 (mod 7) 71771 = 0 (mod 7) 71177 = 1 (mod 7) 71717 = 2 (mod 7) 77171 = 3 (mod 7) 77711 = 4 (mod 7) 77117 = 5 (mod 7) 17177 = 6 (mod 7) 73773 = 0 (mod 7) 77337 = 1 (mod 7) 77373 = 2 (mod 7) 73377 = 3 (mod 7) 37377 = 4 (mod 7) 77733 = 5 (mod 7) 73737 = 6 (mod 7) 79779 = 0 (mod 7) 77799 = 1 (mod 7) 79977 = 2 (mod 7) 77997 = 3 (mod 7) 79797 = 4 (mod 7) 97977 = 5 (mod 7) 77979 = 6 (mod 7) 99911 = 0 (mod 7) 99191 = 1 (mod 7) 91919 = 2 (mod 7) 91199 = 3 (mod 7) 91991 = 4 (mod 7) 19199 = 5 (mod 7) 99119 = 6 (mod 7) 99393 = 0 (mod 7) 99933 = 1 (mod 7) 99339 = 2 (mod 7) 39399 = 3 (mod 7) 93993 = 4 (mod 7) 93399 = 5 (mod 7) 93939 = 6 (mod 7) 97979 = 0 (mod 7) 99779 = 1 (mod 7) 97799 = 2 (mod 7) 99977 = 3 (mod 7) 97997 = 4 (mod 7) 99797 = 5 (mod 7) 79799 = 6 (mod 7) Case 3B: N is a near-repdigit (one digit is different from the others). We show that a near-repunit cannot be prime if it has 17 or more digits. Suppose that N = aaa...ab, where a is repeated 16 or more times. Then the numbers N - (b-a) + (b-a)*10^k are permutations of N for k = 0, 1, 2, ..., 16. These numbers cover all congruence classes modulo 17, since 10 is a primitive root. Therefore, 17 divides one of these numbers. We check (using the Miller-Rabin primality test) that the following numbers are NOT prime. 1111113 1111117 1111119 3313333 3333337 3333339 7777771 7777773 7777779 9999919 9999993 9999997 11111113 11111711 11111191 33333313 33333337 33333339 77777771 77777773 77777779 99999991 99999993 99999997 111111311 111111117 111111119 333333331 333333337 333333339 777777771 777777737 777777779 999999991 999999993 999999997 1111111113 1111111117 1111111119 3333333331 3333333337 3333333339 7777777771 7777777773 7777777779 9999999991 9999999993 9999999997 11111111311 11111111117 11111111119 33333333331 33333333337 33333333339 77777777771 77777777773 77777777779 99999999991 99999999993 99999999997 111111111113 111111111117 111111111119 333333333331 333333333337 333333333339 777777777771 777777777737 777777777779 999999999991 999999999993 999999999997 1111111111113 1111111111117 1111111111119 3333333333331 3333333333337 3333333333339 7777777777717 7777777777773 7777777777779 9999999999991 9999999999993 9999999999997 11111111111113 11111111111117 11111111111119 33333333333331 33333333333337 33333333333339 77777777777771 77777777777773 77777777777779 99999999999991 99999999999993 99999999999997 111111111111113 111111111111117 111111111111119 333333333333331 333333333333337 333333333333339 777777777777771 777777777777737 777777777777779 999999999999991 999999999999993 999999999999997 1111111111111113 1111111111111117 1111111111111119 3333333333333331 3333333333333337 3333333333333339 7777777777777771 7777777777777773 7777777777777779 9999999999999991 9999999999999993 9999999999999997 QED.