The simplest way to check is by going to an IV checker. Check the IVs. If it has an excessive amount of "Simply Can't be beat" IVs, then I'd say it is hacked. You landed yourself a breeding Pokemon.
Of course, it will probably pass all the checks, so whether or not you use it is completely up to your own moral compass.
If I were assessing this Pokemon myself, the chances of getting this fella using the Dexnav and a Shiny Stone is 1 in 180,000. With 3 perfect IVs, 1 in 12,000,000 (because Dex Nav makes every fifth Pokemon "special" with potential, very rarely 3 perfect IVs). With 5 Perfect IVs, you are looking at 1 in 20 billion or so. 6 perfect IVS? 1/32 of those 20 billion Pokemon would have those stats.
I think from the info you have given, it is hacked.