521684066021 has 4 divisors (see below), whose sum is σ = 521708464044. Its totient is φ = 521659668000.

The previous prime is 521684065979. The next prime is 521684066039. The reversal of 521684066021 is 120660486125.

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 218621704900 + 303062361121 = 467570^2 + 550511^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-521684066021 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 521684066021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (521684066521) 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, 12166910 + ... + 12209711.

It is an arithmetic number, because the mean of its divisors is an integer number (130427116011).

Almost surely, 2^521684066021 is an apocalyptic number.

It is an amenable number.

521684066021 is a deficient number, since it is larger than the sum of its proper divisors (24398023).

521684066021 is a wasteful number, since it uses less digits than its factorization.

521684066021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24398022.

The product of its (nonzero) digits is 138240, while the sum is 41.

The spelling of 521684066021 in words is "five hundred twenty-one billion, six hundred eighty-four million, sixty-six thousand, twenty-one".