How many bytes make up 1 megabytes?

Sometimes a million. Sometimes 2^20 = 1024 x 1024, a little bit more. Both usages occur.

1024 kilobytes

1000000 bytes make a megabyte

1,048,576 bytes in a megabyte. 8 bits in each byte Thus 8,388,608 bits in a megabyte (MB)

1 megabyte = 1 048 576 bytes