21404224 has 56 divisors (see below), whose sum is σ = 45646848. Its totient is φ = 9922560.

The previous prime is 21404213. The next prime is 21404263. The reversal of 21404224 is 42240412.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 111969 + ... + 112159.

Almost surely, 2^21404224 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 21404224, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22823424).

21404224 is an abundant number, since it is smaller than the sum of its proper divisors (24242624).

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

21404224 is a wasteful number, since it uses less digits than its factorization.

21404224 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 323 (or 313 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 19.

The square root of 21404224 is about 4626.4699285741. The cubic root of 21404224 is about 277.6513753546.

Adding to 21404224 its reverse (42240412), we get a palindrome (63644636).

The spelling of 21404224 in words is "twenty-one million, four hundred four thousand, two hundred twenty-four".