21723224 has 16 divisors (see below), whose sum is σ = 42502320. Its totient is φ = 10389280.

The previous prime is 21723211. The next prime is 21723227. The reversal of 21723224 is 42232712.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a self number, because there is not a number n which added to its sum of digits gives 21723224.

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, 58847 + ... + 59214.

It is an arithmetic number, because the mean of its divisors is an integer number (2656395).

Almost surely, 2^21723224 is an apocalyptic number.

It is an amenable number.

21723224 is a deficient number, since it is larger than the sum of its proper divisors (20779096).

21723224 is a wasteful number, since it uses less digits than its factorization.

21723224 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 118090 (or 118086 counting only the distinct ones).

The product of its digits is 1344, while the sum is 23.

The square root of 21723224 is about 4660.8179539647. The cubic root of 21723224 is about 279.0239142239.

Adding to 21723224 its reverse (42232712), we get a palindrome (63955936).

The spelling of 21723224 in words is "twenty-one million, seven hundred twenty-three thousand, two hundred twenty-four".