21235431221 has 16 divisors (see below), whose sum is σ = 23324889600. Its totient is φ = 19243193088.

The previous prime is 21235431193. The next prime is 21235431247. The reversal of 21235431221 is 12213453212.

It is a cyclic number.

It is not a de Polignac number, because 21235431221 - 2³⁴ = 4055562037 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 (21235431281) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 116996 + ... + 236978.

It is an arithmetic number, because the mean of its divisors is an integer number (1457805600).

Almost surely, 2^21235431221 is an apocalyptic number.

It is an amenable number.

21235431221 is a deficient number, since it is larger than the sum of its proper divisors (2089458379).

21235431221 is a wasteful number, since it uses less digits than its factorization.

21235431221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 120388.

The product of its digits is 2880, while the sum is 26.

Adding to 21235431221 its reverse (12213453212), we get a palindrome (33448884433).

The spelling of 21235431221 in words is "twenty-one billion, two hundred thirty-five million, four hundred thirty-one thousand, two hundred twenty-one".