21000011021 has 4 divisors (see below), whose sum is σ = 22909102944. Its totient is φ = 19090919100.

The previous prime is 21000010991. The next prime is 21000011027. The reversal of 21000011021 is 12011000012.

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 not a de Polignac number, because 21000011021 - 2¹⁰ = 21000009997 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 (21000011027) 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, 954545945 + ... + 954545966.

It is an arithmetic number, because the mean of its divisors is an integer number (5727275736).

Almost surely, 2^21000011021 is an apocalyptic number.

It is an amenable number.

21000011021 is a deficient number, since it is larger than the sum of its proper divisors (1909091923).

21000011021 is a wasteful number, since it uses less digits than its factorization.

21000011021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1909091922.

The product of its (nonzero) digits is 4, while the sum is 8.

Adding to 21000011021 its reverse (12011000012), we get a palindrome (33011011033).

The spelling of 21000011021 in words is "twenty-one billion, eleven thousand, twenty-one".