2197 ^ p 2 -1 = 28,561^p 2 -13

2197^(p²-1) = 28,561^(p²-13)  

(13^3) ^(p²-1) = (13^4) ^(p²-13)

[13]^{3p²-3)  = [13]^(4p²-52)       equate exponents

{3p²-3)  = (4p²-52)   rearrange

49 = p^2        take both roots

± 7  = p