21204403021 has 8 divisors (see below), whose sum is σ = 21436331840. Its totient is φ = 20972746368.

The previous prime is 21204402997. The next prime is 21204403043. The reversal of 21204403021 is 12030440212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21204403021 - 2¹³ = 21204394829 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 21204403021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21204403421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 90640 + ... + 224998.

It is an arithmetic number, because the mean of its divisors is an integer number (2679541480).

Almost surely, 2^21204403021 is an apocalyptic number.

It is an amenable number.

21204403021 is a deficient number, since it is larger than the sum of its proper divisors (231928819).

21204403021 is a wasteful number, since it uses less digits than its factorization.

21204403021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 136083.

The product of its (nonzero) digits is 384, while the sum is 19.

Adding to 21204403021 its reverse (12030440212), we get a palindrome (33234843233).

The spelling of 21204403021 in words is "twenty-one billion, two hundred four million, four hundred three thousand, twenty-one".