Perfect squares have an odd number of factors. There are 31 perfect squares less than 1000.
31 easy
Literally every single even number less than 1000 is a composite number other than 2 which is prime.
By definition, a prime number has exactly two factors. So, there are no prime numbers with exactly three factors.
Every second number greater than 2 is an even number.
512 = 29 or 768 = 28*3 have 9 prime factors each.
Four of them.
There are 31 numbers less than 1,000 which have an odd number of factors. They are: 1,4,9,16,25,36,49,64,81,100,121,144,169,196,225,256,289,324,361,400,441,484,529,576,625,676,729,784,841,900,961.
210 has 4, which is the maximum possible. There are other numbers with 4 different prime factors.
1000 more is 577233 1000 less is 575233
11
840
There are 12 numbers less than 150 which have an odd number of factors: 1,4,9,16,25,36,49,64,81,100,121,144.
577233 and 575233 respectively
There are four odd numbers less that 100 that have 6 factor. This does not compare with even numbers that have 12 factors!
1000 more:7735 1000 less:5735
The three greatest whole numbers less than 200 that each have an odd number of factors are 144, 169 and 196.
If you take away 1000 from 503000019 you get 502999019.If you add 1000 to 503000019 you get 503001019.
3, 9, 27, 81, 243, 729