I'm a number. The difference between me and my checksum is 36 and I am the product of two adjacent numbers. Which number am I?
I know it's pretty simple but one that just came to my mind right now =D
I think you are
$42$
Checksum
$42 - 4 - 2 = 36$
Product
$42 = 6 \times 7$
Method
It suffices to check the first few numbers which are the product of adjacent integers as the number itself grows much faster than the checksum and will surpass $36$ early on.