Displayed precision ≠ Stored precision
Note that the block timestamp is stored as a 4-byte number of seconds since 1970-01-01T00:00 UTC (the Unix epoch). However Blockchain.com show this in a more human readable form rounded or truncated to the nearest minute (2011-05-21 18:26). So if you convert that human readable time back to an integer, you will get a value that is different by a number of seconds between 0 and 59
See Wikipedia article on endianness. There are two possible orderings of the bytes of a multi-byte integer. You can start with least significant byte (LSB) or with most significant byte (MSB). Internet standard "Network Order" is big-endian. X86 architecture computers use little-endian byte-order. Some other hardware architectures use big-endian byte-order.
Bitcoin mostly uses little endian. Even for data transmitted over the Internet. See documentation for block hashing. Note that it talks about the use of big-endian for hexadecimal display of values and little-endian for storage.
Timestamps are not accurate
See Why don't the timestamps in the block chain always increase?
A timestamp is accepted as valid if it is greater than the median timestamp of previous 11 blocks, and less than the network-adjusted time + 2 hours. "Network-adjusted time" is the median of the timestamps returned by all nodes connected to you.
So don't be surprised if later blocks sometimes have earlier timestamps. Children can be older than their parents.