521717221 has 4 divisors (see below), whose sum is σ = 539707500. Its totient is φ = 503726944.

The previous prime is 521717191. The next prime is 521717227. The reversal of 521717221 is 122717125.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 156525121 + 365192100 = 12511^2 + 19110^2 .

It is a cyclic number.

It is not a de Polignac number, because 521717221 - 2⁹ = 521716709 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 521717221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (521717227) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8995096 + ... + 8995153.

It is an arithmetic number, because the mean of its divisors is an integer number (134926875).

Almost surely, 2^521717221 is an apocalyptic number.

It is an amenable number.

521717221 is a deficient number, since it is larger than the sum of its proper divisors (17990279).

521717221 is a wasteful number, since it uses less digits than its factorization.

521717221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17990278.

The product of its digits is 1960, while the sum is 28.

The square root of 521717221 is about 22841.1300289631. The cubic root of 521717221 is about 805.0293681659.

The spelling of 521717221 in words is "five hundred twenty-one million, seven hundred seventeen thousand, two hundred twenty-one".