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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.

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Q: How many 3 digit numbers have even no of factors?
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How many three digit even numbers are possible if the left digit cannot be zero?

450


How many four digit whole numbers are there such that the thousand digit is odd the hundreds digit is even and all four digits are different?

5*5*4*4 = 400


How many 5 digit numbers are odd?

The first 5 digit number is 10,000 and the last is 99,999. Thus there are 90,000 numbers between that range. Half of them are odd & half are even. 45,000 each


How many even 3-digit numbers can be formed from the digits 1 2 3 and 5 if each digit can be used only once?

The final digit must be a 2 to form an even number. The first digit may be any of three remaining digits (1, 3, 5) while the second digit may be any of the two remaining digits. All together, that makes 3*2 = 6 distinct even numbers.


How many even 6 digit numbers are there?

Counting just positive numbers, we have all numbers from 100000 to 999999, the difference is 899,999, but because we count both the starting and ending number, we have to add 1 to this, which makes it 900,000 numbers. Of course if you want to include also negative numbers that makes it 1,800,000. And because we want only EVEN numbers these totals would be divided by 2, so there are 450,000 positive, even, 6 digit numbers and 450,000 negative, even, 6 digit numbers. Total is 900,000. This is considering whole numbers only. If we include ALL numbers than we would also have to count the six digit numbers between 1 and -1... such as .000002 through .999998 thereby doubling again the total to 1.8 million.