521340021 has 12 divisors (see below), whose sum is σ = 756200640. Its totient is φ = 346104360.

The previous prime is 521340013. The next prime is 521340073. The reversal of 521340021 is 120043125.

It is not a de Polignac number, because 521340021 - 2³ = 521340013 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 521339976 and 521340003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (521340821) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 119035 + ... + 123336.

It is an arithmetic number, because the mean of its divisors is an integer number (63016720).

Almost surely, 2^521340021 is an apocalyptic number.

It is an amenable number.

521340021 is a deficient number, since it is larger than the sum of its proper divisors (234860619).

521340021 is a wasteful number, since it uses less digits than its factorization.

521340021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 242616 (or 242613 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 521340021 is about 22832.8715014122. The cubic root of 521340021 is about 804.8353101105.

Adding to 521340021 its reverse (120043125), we get a palindrome (641383146).

The spelling of 521340021 in words is "five hundred twenty-one million, three hundred forty thousand, twenty-one".