21231243221 has 4 divisors (see below), whose sum is σ = 21231886944. Its totient is φ = 21230599500.

The previous prime is 21231243217. The next prime is 21231243239. The reversal of 21231243221 is 12234213212.

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 a cyclic number.

It is not a de Polignac number, because 21231243221 - 2² = 21231243217 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 (21231243211) 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, 269555 + ... + 339296.

It is an arithmetic number, because the mean of its divisors is an integer number (5307971736).

Almost surely, 2^21231243221 is an apocalyptic number.

It is an amenable number.

21231243221 is a deficient number, since it is larger than the sum of its proper divisors (643723).

21231243221 is an equidigital number, since it uses as much as digits as its factorization.

21231243221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 643722.

The product of its digits is 1152, while the sum is 23.

Adding to 21231243221 its reverse (12234213212), we get a palindrome (33465456433).

The spelling of 21231243221 in words is "twenty-one billion, two hundred thirty-one million, two hundred forty-three thousand, two hundred twenty-one".