21123203221 has 4 divisors (see below), whose sum is σ = 21124882944. Its totient is φ = 21121523500.

The previous prime is 21123203219. The next prime is 21123203237. The reversal of 21123203221 is 12230232112.

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 21123203221 - 2¹ = 21123203219 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 (21123203261) 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, 820855 + ... + 846196.

It is an arithmetic number, because the mean of its divisors is an integer number (5281220736).

Almost surely, 2^21123203221 is an apocalyptic number.

It is an amenable number.

21123203221 is a deficient number, since it is larger than the sum of its proper divisors (1679723).

21123203221 is a wasteful number, since it uses less digits than its factorization.

21123203221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1679722.

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

Adding to 21123203221 its reverse (12230232112), we get a palindrome (33353435333).

The spelling of 21123203221 in words is "twenty-one billion, one hundred twenty-three million, two hundred three thousand, two hundred twenty-one".