21235311021 has 4 divisors (see below), whose sum is σ = 28313748032. Its totient is φ = 14156874012.

The previous prime is 21235311007. The next prime is 21235311079. The reversal of 21235311021 is 12011353212.

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 21235311021 - 2⁵ = 21235310989 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 (21235311001) 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, 3539218501 + ... + 3539218506.

It is an arithmetic number, because the mean of its divisors is an integer number (7078437008).

Almost surely, 2^21235311021 is an apocalyptic number.

It is an amenable number.

21235311021 is a deficient number, since it is larger than the sum of its proper divisors (7078437011).

21235311021 is an equidigital number, since it uses as much as digits as its factorization.

21235311021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7078437010.

The product of its (nonzero) digits is 360, while the sum is 21.

Adding to 21235311021 its reverse (12011353212), we get a palindrome (33246664233).

The spelling of 21235311021 in words is "twenty-one billion, two hundred thirty-five million, three hundred eleven thousand, twenty-one".