21232230721 has 4 divisors (see below), whose sum is σ = 22865479252. Its totient is φ = 19598982192.

The previous prime is 21232230709. The next prime is 21232230791. The reversal of 21232230721 is 12703223212.

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 7481385025 + 13750845696 = 86495^2 + 117264^2 .

It is a cyclic number.

It is not a de Polignac number, because 21232230721 - 2⁹ = 21232230209 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21232230791) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 816624246 + ... + 816624271.

It is an arithmetic number, because the mean of its divisors is an integer number (5716369813).

Almost surely, 2^21232230721 is an apocalyptic number.

It is an amenable number.

21232230721 is a deficient number, since it is larger than the sum of its proper divisors (1633248531).

21232230721 is a wasteful number, since it uses less digits than its factorization.

21232230721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1633248530.

The product of its (nonzero) digits is 2016, while the sum is 25.

Adding to 21232230721 its reverse (12703223212), we get a palindrome (33935453933).

The spelling of 21232230721 in words is "twenty-one billion, two hundred thirty-two million, two hundred thirty thousand, seven hundred twenty-one".