21211020021 has 4 divisors (see below), whose sum is σ = 28281360032. Its totient is φ = 14140680012.

The previous prime is 21211019989. The next prime is 21211020119. The reversal of 21211020021 is 12002011212.

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 21211020021 - 2⁵ = 21211019989 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21211019979 and 21211020006.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21211020421) 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, 3535170001 + ... + 3535170006.

It is an arithmetic number, because the mean of its divisors is an integer number (7070340008).

Almost surely, 2^21211020021 is an apocalyptic number.

It is an amenable number.

21211020021 is a deficient number, since it is larger than the sum of its proper divisors (7070340011).

21211020021 is an equidigital number, since it uses as much as digits as its factorization.

21211020021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7070340010.

The product of its (nonzero) digits is 16, while the sum is 12.

Adding to 21211020021 its reverse (12002011212), we get a palindrome (33213031233).

The spelling of 21211020021 in words is "twenty-one billion, two hundred eleven million, twenty thousand, twenty-one".