21723223 has 4 divisors (see below), whose sum is σ = 21894400. Its totient is φ = 21552048.

The previous prime is 21723211. The next prime is 21723227. The reversal of 21723223 is 32232712.

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 21723223 - 2²¹ = 19626071 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21723194 and 21723203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21723227) 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, 85398 + ... + 85651.

It is an arithmetic number, because the mean of its divisors is an integer number (5473600).

Almost surely, 2^21723223 is an apocalyptic number.

21723223 is a deficient number, since it is larger than the sum of its proper divisors (171177).

21723223 is a wasteful number, since it uses less digits than its factorization.

21723223 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 171176.

The product of its digits is 1008, while the sum is 22.

The square root of 21723223 is about 4660.8178466874. The cubic root of 21723223 is about 279.0239099424.

Adding to 21723223 its reverse (32232712), we get a palindrome (53955935).

The spelling of 21723223 in words is "twenty-one million, seven hundred twenty-three thousand, two hundred twenty-three".