21123232021 has 4 divisors (see below), whose sum is σ = 21638432844. Its totient is φ = 20608031200.

The previous prime is 21123231953. The next prime is 21123232049. The reversal of 21123232021 is 12023232112.

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 4510599921 + 16612632100 = 67161^2 + 128890^2 .

It is a cyclic number.

It is not a de Polignac number, because 21123232021 - 2¹⁷ = 21123100949 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 21123232021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21123232051) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 257600350 + ... + 257600431.

It is an arithmetic number, because the mean of its divisors is an integer number (5409608211).

Almost surely, 2^21123232021 is an apocalyptic number.

It is an amenable number.

21123232021 is a deficient number, since it is larger than the sum of its proper divisors (515200823).

21123232021 is an equidigital number, since it uses as much as digits as its factorization.

21123232021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 515200822.

The product of its (nonzero) digits is 288, while the sum is 19.

Adding to 21123232021 its reverse (12023232112), we get a palindrome (33146464133).

Subtracting from 21123232021 its reverse (12023232112), we obtain a palindrome (9099999909).

It can be divided in two parts, 211232 and 32021, that added together give a triangular number (243253 = T₆₉₇).

The spelling of 21123232021 in words is "twenty-one billion, one hundred twenty-three million, two hundred thirty-two thousand, twenty-one".