21235927021 has 4 divisors (see below), whose sum is σ = 21238332444. Its totient is φ = 21233521600.

The previous prime is 21235926997. The next prime is 21235927061. The reversal of 21235927021 is 12072953212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 12891104521 + 8344822500 = 113539^2 + 91350^2 .

It is a cyclic number.

It is not a de Polignac number, because 21235927021 - 2⁷ = 21235926893 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 (21235927061) 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, 1189420 + ... + 1207141.

It is an arithmetic number, because the mean of its divisors is an integer number (5309583111).

Almost surely, 2^21235927021 is an apocalyptic number.

It is an amenable number.

21235927021 is a deficient number, since it is larger than the sum of its proper divisors (2405423).

21235927021 is an equidigital number, since it uses as much as digits as its factorization.

21235927021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2405422.

The product of its (nonzero) digits is 15120, while the sum is 34.

The spelling of 21235927021 in words is "twenty-one billion, two hundred thirty-five million, nine hundred twenty-seven thousand, twenty-one".