21224704 has 36 divisors (see below), whose sum is σ = 44867844. Its totient is φ = 9986048.

The previous prime is 21224689. The next prime is 21224737. The reversal of 21224704 is 40742212.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 11289600 + 9935104 = 3360^2 + 3152^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1914 + ... + 6790.

It is an arithmetic number, because the mean of its divisors is an integer number (1246329).

Almost surely, 2^21224704 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21224704, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22433922).

21224704 is an abundant number, since it is smaller than the sum of its proper divisors (23643140).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21224704 is an equidigital number, since it uses as much as digits as its factorization.

21224704 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4910 (or 4896 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 22.

The square root of 21224704 is about 4607.0276751936. The cubic root of 21224704 is about 276.8729623780.

Adding to 21224704 its reverse (40742212), we get a palindrome (61966916).

The spelling of 21224704 in words is "twenty-one million, two hundred twenty-four thousand, seven hundred four".