21004424 has 48 divisors (see below), whose sum is σ = 47548800. Its totient is φ = 8519904.

The previous prime is 21004387. The next prime is 21004447. The reversal of 21004424 is 42440012.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 19697 + ... + 20735.

It is an arithmetic number, because the mean of its divisors is an integer number (990600).

Almost surely, 2^21004424 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 21004424, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23774400).

21004424 is an abundant number, since it is smaller than the sum of its proper divisors (26544376).

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

21004424 is a wasteful number, since it uses less digits than its factorization.

21004424 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1090 (or 1067 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 17.

The square root of 21004424 is about 4583.0583675096. The cubic root of 21004424 is about 275.9117900565.

Adding to 21004424 its reverse (42440012), we get a palindrome (63444436).

The spelling of 21004424 in words is "twenty-one million, four thousand, four hundred twenty-four".