A second is our base unit of time—base, but not the smallest. A base unit is a unit defined on its own terms upon which other units are based. That means that all our other units, such as minutes, hours, nanoseconds, and so on, are all based on seconds. You may already know that there are 60 minutes in an hour, but how many seconds is that? To figure it out, we’ll need to multiply. 60 seconds in one minute and 60 minutes in one hour means that 1hour=60*60. Calculate that out and you’ll find that 1 hour = 3,600 seconds.

Source: PrepScholar