21003648 has 64 divisors (see below), whose sum is σ = 56548800. Its totient is φ = 6906368.

The previous prime is 21003637. The next prime is 21003659. The reversal of 21003648 is 84630012.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21003637) and next prime (21003659).

It is a tau number, because it is divible by the number of its divisors (64).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

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, 31543 + ... + 32201.

It is an arithmetic number, because the mean of its divisors is an integer number (883575).

Almost surely, 2^21003648 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 21003648, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28274400).

21003648 is an abundant number, since it is smaller than the sum of its proper divisors (35545152).

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

21003648 is an equidigital number, since it uses as much as digits as its factorization.

21003648 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 759 (or 747 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 24.

The square root of 21003648 is about 4582.9737071033. The cubic root of 21003648 is about 275.9083921979.

The spelling of 21003648 in words is "twenty-one million, three thousand, six hundred forty-eight".