21223231 has 4 divisors (see below), whose sum is σ = 21433464. Its totient is φ = 21013000.

The previous prime is 21223219. The next prime is 21223261. The reversal of 21223231 is 13232212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21223231 - 2¹⁹ = 20698943 is a prime.

It is a super-2 number, since 2×21223231² = 900851068158722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21223261) 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, 104965 + ... + 105166.

It is an arithmetic number, because the mean of its divisors is an integer number (5358366).

Almost surely, 2^21223231 is an apocalyptic number.

21223231 is a deficient number, since it is larger than the sum of its proper divisors (210233).

21223231 is a wasteful number, since it uses less digits than its factorization.

21223231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 210232.

The product of its digits is 144, while the sum is 16.

The square root of 21223231 is about 4606.8678079580. The cubic root of 21223231 is about 276.8665572112.

Adding to 21223231 its reverse (13232212), we get a palindrome (34455443).

The spelling of 21223231 in words is "twenty-one million, two hundred twenty-three thousand, two hundred thirty-one".