Is there a way to prove or disprove:
For any given number $k$,there must be prime $p$ that satisfied $10, 100,\dots,10^{p-1}$ are complete residue system modulo $p$.
for example: If k = 6, I can choose p = 7 or 17 10¹≡3,10²≡2,10³≡6,10⁴≡4,10⁵≡5,10⁶≡1 (mod 7) 10¹≡10,10²≡15,10³≡14,10⁴≡4,10⁵≡6,10⁶≡9,10⁷≡5,...10¹⁵≡8,10¹⁶≡12 (mod 17)
but if I choose p = 11 or 13 10¹≡10,10²≡1,10³≡10,10⁴≡1... (mod 11) 10¹≡10,10²≡9,10³≡12,10⁴≡3,10⁵≡4,10⁶≡1,10⁷≡10...(mod 13) then that is not a complete residue system
I know 7, 17,19, 23, 29, 47, 59 are the type of primes, and it seems related to Fermat little theorem? It is same to prove: for 1≦n≦(p-1), n satisfied 10ⁿ≡1 (mod p) is only (p-1), numbers of primes of the type are indefinitely.
Thank you very much for your help.