521405512421 has 4 divisors (see below), whose sum is σ = 531243352332. Its totient is φ = 511567672512.

The previous prime is 521405512393. The next prime is 521405512427. The reversal of 521405512421 is 124215504125.

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 309703380100 + 211702132321 = 556510^2 + 460111^2 .

It is a cyclic number.

It is not a de Polignac number, because 521405512421 - 2¹⁸ = 521405250277 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (521405512427) 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, 4918919876 + ... + 4918919981.

It is an arithmetic number, because the mean of its divisors is an integer number (132810838083).

Almost surely, 2^521405512421 is an apocalyptic number.

It is an amenable number.

521405512421 is a deficient number, since it is larger than the sum of its proper divisors (9837839911).

521405512421 is an equidigital number, since it uses as much as digits as its factorization.

521405512421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9837839910.

The product of its (nonzero) digits is 16000, while the sum is 32.

The spelling of 521405512421 in words is "five hundred twenty-one billion, four hundred five million, five hundred twelve thousand, four hundred twenty-one".