100 x 365 = 36500
100 times 365 is 36500. Multiplying by 100 moves 365 two places up, adding two zeros. That is the number of days in 100 years, if none of them were leap years.
100 × 365 = 36,500
Adding 100 to itself 365 times gives the same answer.
The working
100 x 365 = 36500. Only the 100 is round, so leave 365 alone and give it two zeros. Broken up the long way it is 300 x 100 plus 60 x 100 plus 5 x 100, which is 30000 plus 6000 plus 500. The middle piece is 100 x 60.
36500 is not quite a century
365 days is a common year, so 36500 looks like the length of 100 years. It is short. The Gregorian calendar adds a leap day in most years divisible by four, so the century from 2001 to 2100 actually runs 36524 days, and the century from 1901 to 2000 ran 36525 because the year 2000 kept its leap day. The plain multiplication always comes in 24 or 25 days under a real century.
What 36500 divides by
365 is not prime. It is 5 x 73, which makes 36500 the same as 4 x 125 x 73. That 73 is stubborn: 36500 will not split evenly into thirds or sevenths, which is worth knowing before you try to break it into months or weeks.
Nearby totals
A thousand years of the same kind is 1000 x 365, or 365000 days. Counting in weeks instead gives 100 x 52. Both sit with the others on the multiplication answers index.