21004234021 has 4 divisors (see below), whose sum is σ = 21006247392. Its totient is φ = 21002220652.

The previous prime is 21004234003. The next prime is 21004234033. The reversal of 21004234021 is 12043240012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21004234021 - 2⁵ = 21004233989 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 21004234021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21004234051) 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 3 ways as a sum of consecutive naturals, for example, 990955 + ... + 1011928.

It is an arithmetic number, because the mean of its divisors is an integer number (5251561848).

Almost surely, 2^21004234021 is an apocalyptic number.

It is an amenable number.

21004234021 is a deficient number, since it is larger than the sum of its proper divisors (2013371).

21004234021 is a wasteful number, since it uses less digits than its factorization.

21004234021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2013370.

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

Adding to 21004234021 its reverse (12043240012), we get a palindrome (33047474033).

It can be divided in two parts, 21004 and 234021, that added together give a square (255025 = 505²).

The spelling of 21004234021 in words is "twenty-one billion, four million, two hundred thirty-four thousand, twenty-one".