Calculate hash of block header

Question

I'm trying to calculate the hash of block #502871. This is the block:

{
"result": {
    "hash": "00000000000000000020cf2bdc6563fb25c424af588d5fb7223461e72715e4a9",
    "confirmations": 35,
    "strippedsize": 976261,
    "size": 1064277,
    "weight": 3993060,
    "height": 502871,
    "version": 536870912,
    "versionHex": "20000000",
    "merkleroot": "871148c57dad60c0cde483233b099daa3e6492a91c13b337a5413a4c4f842978",
    "tx": [
        "6fef5a38c0a76d4bfb6644afed809fe760abcbe9c1e030b7b09bd876f8d28765",
        "2506559cd75c9537108c63adddf6910eaa2c12e9e129b75528dd5dbff8e6cef3",
        ...
        "b136d220a049fd9a42261153c7d5e21e12b791c27eed9cb9e41acaea672a6af5",
        "7dbaf4d2b31d4a000b9f2028dd350e46da427b8c1721f030af67d5e47f322da5"
    ],
    "time": 1515252561,
    "mediantime": 1515249802,
    "nonce": 45291998,
    "bits": "180091c1",
    "difficulty": 1931136454487.716,
    "chainwork": "000000000000000000000000000000000000000000e0ef1d9aa7eeab21ce8628",
    "previousblockhash": "00000000000000000061abcd4f51d81ddba5498cff67fed44b287de0990b7266",
    "nextblockhash": "00000000000000000075e23616edab2b743425a064c282a7745ad38d05806e80"
},
"error": null,
"id": null

}

So according to https://en.bitcoin.it/wiki/Block_hashing_algorithm I need these values:

 versionHex: 20000000
 previousblockhash: 
 00000000000000000061abcd4f51d81ddba5498cff67fed44b287de0990b7266
 merkleroot: 871148c57dad60c0cde483233b099daa3e6492a91c13b337a5413a4c4f842978
 time: 1515252561
 bits: 180091c1
 nonce: 45291998

Formatting the values I get:

version: 02000000
previousblockhash: 66720b99e07d284bd4fe67ff8c49a5db1dd8514fcdab61000000000000000000
merkleroot: 7829844f4c3a41a537b3131ca992643eaa9d093b2383e4cdc060ad7dc5481187
time: (5A50EB51)_16 -> 51eb505a
bits: c1910018
nonce: (02B319DE)_16 -> de19b302

So my block header is:

0200000066720b99e07d284bd4fe67ff8c49a5db1dd8514fcdab610000000000000000007829844f4c3a41a537b3131ca992643eaa9d093b2383e4cdc060ad7dc548118751eb505ac1910018de19b302

And when I calculate the hash:

from hashlib import sha256
import hashlib    
header = "0200000066720b99e07d284bd4fe67ff8c49a5db1dd8514fcdab610000000000000000007829844f4c3a41a537b3131ca992643eaa9d093b2383e4cdc060ad7dc548118751eb505ac1910018de19b302".decode('hex')
print sha256(sha256(header).digest()).digest()[::-1].encode('hex')

The result is

0a80d313f7c8bab35b1442a194516c3ddff9ddc674c752ccfaffb1c83866a073

But not the the expected one:

00000000000000000020cf2bdc6563fb25c424af588d5fb7223461e72715e4a9

Please, what am I doing wrong? Thanks.

Answer 1

The version is wrong:

I have 02000000

But the one that appears on the block is

Version 0x20000000

Doing the formatting:

00000020  

Calculating the hash of the block:

from hashlib import sha256
import hashlib
header = "0000002066720b99e07d284bd4fe67ff8c49a5db1dd8514fcdab610000000000000000007829844f4c3a41a537b3131ca992643eaa9d093b2383e4cdc060ad7dc548118751eb505ac1910018de19b302".decode('hex')
print sha256(sha256(header).digest()).digest()[::-1].encode('hex')

And the answer is:

00000000000000000020cf2bdc6563fb25c424af588d5fb7223461e72715e4a9

That is the original hash in the block:

00000000000000000020cf2bdc6563fb25c424af588d5fb7223461e72715e4a9