Total number of 2-digit numbers = (99 - 9) = 90 of them
Every number that isn't a perfect square has an even number of factors.
2-digit numbers that are perfect squares: 16, 25, 36, 49, 64, and 81 = 6 of them
Remaining 2-digit numbers = (99 - 6) = 93 .
100
500 or so.
There are 4500 such numbers.
Half of them. Every other number from 0 to 99998 is even. Since there are 90,000 five digit numbers, that means that 45,000 of them are even.
There are 450 even three-digit integers, from 100 to 998. This excludes numbers with leading zeroes (000 to 099).
With a total of 90,000 five digit numbers, we can conclude that there is 45,000 EVEN five digit numbers.
878 three digit numbers have an even number of factors. Every factor of a number has a pair, so there ought to be an even number of factors for every number. However, if a pair of the factors are the same number, then there will be an odd number of factors, that is if the number is a perfect square. Assuming three digit numbers are 100 to 999: From 100 to 999, the perfect squares are 102 = 100 to 312 = 961, a total of 31-10+1 = 22 numbers. So of the 999-100+1 = 900 three digit numbers, 22 have an odd number of factors, so 900-22 = 878 have an even number of factors.
All of them.
100
4,000 even numbers, 4,000 odd numbers.
2240
There are 450 even three-digit integers, from 100 to 998. This excludes numbers with leading zeroes (000 to 099).
500 or so.
There are 4500 such numbers.
There are 449999 such numbers.
Half of them. Every other number from 0 to 99998 is even. Since there are 90,000 five digit numbers, that means that 45,000 of them are even.
There are 450 even three-digit integers, from 100 to 998. This excludes numbers with leading zeroes (000 to 099).