Number Gossip
(Enter a number and I'll tell you everything you wanted to know about it but were afraid to ask.)
Unique Properties of 900
- 900 is the square of the smallest sphenic number. It is a product of squares of the first three primes
- 900 is the smallest number whose sum of proper square divisors is a square greater than 1
- 900 is the smallest number n such that φ(n)τ(n) divides n2, but neither τ(n) nor φ(n) divides n
Rare Properties of 900
The number n is a square if it is the square of an integer.
Common Properties of 900
The number n is abundant if the sum of all its positive divisors except itself is more than n.
They are abundant above perfection, not to mention deficiency. See perfect and deficient numbers.
A positive integer greater than 1 that is not prime is called composite.
Composite numbers are opposite to prime numbers.
A number is even if it is divisible by 2.
Numbers that are not even are odd. Compare with another pair -- evil and odious numbers.
The number n is evil if it has an even number of 1's in its binary expansion.
Guess what odious numbers are.
An integer n is powerful if for every prime p dividing n, p2 also divides n.
How much power? They all can be written as a2 b3.
The number n is practical if all numbers strictly less than n are sums of distinct divisors of n.