For a signature, or to “move his stash” as you said? The Genesis coinbase itself can’t be moved; it is not sent to that address, but rather, in P2PK to a public key that people convert to that P2PKH address as an anachronism.
18.53375545 BTC from that address can be moved, if you have the wallet (private key) of Satoshi.
The correct (movable) amount is listed by Block Stream Explorer (note how the 50 BTC mining reward transaction is not listed here for the same address):
https://blockstream.info/address/1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa