521201664 has 72 divisors (see below), whose sum is σ = 1505379330. Its totient is φ = 173727744.

The previous prime is 521201651. The next prime is 521201683. The reversal of 521201664 is 466102125.

It can be written as a sum of positive squares in only one way, i.e., 466560000 + 54641664 = 21600^2 + 7392^2 .

It is a tau number, because it is divible by the number of its divisors (72).

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4294 + ... + 32570.

Almost surely, 2^521201664 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 521201664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (752689665).

521201664 is an abundant number, since it is smaller than the sum of its proper divisors (984177666).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

521201664 is a wasteful number, since it uses less digits than its factorization.

521201664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28305 (or 28282 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 27.

The square root of 521201664 is about 22829.8415237601. The cubic root of 521201664 is about 804.7641061318.

Adding to 521201664 its reverse (466102125), we get a palindrome (987303789).

The spelling of 521201664 in words is "five hundred twenty-one million, two hundred one thousand, six hundred sixty-four".