521721252 has 108 divisors (see below), whose sum is σ = 1477787220. Its totient is φ = 154941696.

The previous prime is 521721191. The next prime is 521721271. The reversal of 521721252 is 252127125.

It can be written as a sum of positive squares in 6 ways, for example, as 141705216 + 380016036 = 11904^2 + 19494^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 174958 + ... + 177914.

It is an arithmetic number, because the mean of its divisors is an integer number (13683215).

Almost surely, 2^521721252 is an apocalyptic number.

521721252 is a gapful number since it is divisible by the number (52) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 521721252, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (738893610).

521721252 is an abundant number, since it is smaller than the sum of its proper divisors (956065968).

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

521721252 is a wasteful number, since it uses less digits than its factorization.

521721252 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3022 (or 3004 counting only the distinct ones).

The product of its digits is 2800, while the sum is 27.

The square root of 521721252 is about 22841.2182687351. The cubic root of 521721252 is about 805.0314414889.

Adding to 521721252 its reverse (252127125), we get a palindrome (773848377).

The spelling of 521721252 in words is "five hundred twenty-one million, seven hundred twenty-one thousand, two hundred fifty-two".