Did you try checking how many transactions are associated with these addresses? If they were used thousands of times it's definitely an exchange as no mere mortal can use an address that many times.
This address in particular has 7800+ transactions.
1A8JiWcwvpY7tAopUkSnGuEYHmzGYfZPiq
I am almost 100% convinced that the address does not belong to an exchange. I believe it is somehow connected to Blockchain.com wallet, but I don't know how (yet). Did you check the links I provided above, where this address is mentioned? Especially
this one.
Besides, if you check this address using the Search function of the forum, you'll find plenty of topics where it is mentioned. Maybe one of the most relevant post this
this one, made by piuk, which is also the OP of the topic
Blockchain.info - Bitcoin Block explorer & Currency Statistics:
All the search results from the forum, all the 3 links I mentioned in OP about this address and, ultimately, the above quote make me think that this address is connected to Blockchain.com wallet. And if this is true, then I come back to the other two address from OP:
1GENmtQhhFhrEKLqV8JRftxYWdCdDxRG7D
1EGNSasgE9uwrok6vviw4Bo7nSu1XgKubY
Considering that when those addresses sent funds, each time they sent the funds to a destination but also 0.005 BTC to 1A8JiWcwvpY7tAopUkSnGuEYHmzGYfZPiq, is it possible then that those addresses are also Blockchain.com addresses?