21523223 has 4 divisors (see below), whose sum is σ = 21713808. Its totient is φ = 21332640.

The previous prime is 21523171. The next prime is 21523261. The reversal of 21523223 is 32232512.

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 21523223 - 2¹⁶ = 21457687 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21523195 and 21523204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21523273) 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, 95123 + ... + 95348.

It is an arithmetic number, because the mean of its divisors is an integer number (5428452).

Almost surely, 2^21523223 is an apocalyptic number.

21523223 is a deficient number, since it is larger than the sum of its proper divisors (190585).

21523223 is a wasteful number, since it uses less digits than its factorization.

21523223 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 190584.

The product of its digits is 720, while the sum is 20.

The square root of 21523223 is about 4639.3127723834. The cubic root of 21523223 is about 278.1649685942.

Adding to 21523223 its reverse (32232512), we get a palindrome (53755735).

The spelling of 21523223 in words is "twenty-one million, five hundred twenty-three thousand, two hundred twenty-three".