There are 28 Gold Bolts in Ratchet & Clank (2016 PS4 Remake). Finding all locations unlocks the Ultimate Explorer trophy.
To Find them all you need to get some gadgets. Do all optional objectives and pick up every gadget. Then travel back to each planet and pick up the gold bolts.
There is also a gadget called "Map-O-Matic" that reveals all gold bolt locations on the map. But even with their location revealed some can still be tricky to reach.
All planets in the game:
Veldin
Novalis
Kerwan
Aridia
Nebula G34
Rilgar
Batalia
Gaspar
Pokitaru
Quartu
Kalebo III
Deplanetizer