Adding to 521640 its reverse (46125), we get a palindrome (567765).
It is a happy number.
521640 is a `hidden beast` number, since 5 + 21 + 640 = 666.
521640 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.
It is a congruent number.
521640 is an untouchable number, because it is not equal to the sum of proper divisors of any number.
2521640 is an apocalyptic number.
It is an amenable number.
It is a practical number, because each smaller number is the sum of distinct divisors of 521640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1045440).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
521640 is a wasteful number, since it uses less digits than its factorization.
521640 is an evil number, because the sum of its binary digits is even.
The square root of 521640 is about 722.2464953186. The cubic root of 521640 is about 80.4989647900.
The spelling of 521640 in words is "five hundred twenty-one thousand, six hundred forty".