21388512 has 48 divisors (see below), whose sum is σ = 57964032. Its totient is φ = 6898560.

The previous prime is 21388469. The next prime is 21388517. The reversal of 21388512 is 21588312.

It is a tau number, because it is divible by the number of its divisors (48).

It is a self number, because there is not a number n which added to its sum of digits gives 21388512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21388517) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 618 + ... + 6569.

It is an arithmetic number, because the mean of its divisors is an integer number (1207584).

Almost surely, 2^21388512 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 21388512, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28982016).

21388512 is an abundant number, since it is smaller than the sum of its proper divisors (36575520).

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

21388512 is a wasteful number, since it uses less digits than its factorization.

21388512 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7231 (or 7223 counting only the distinct ones).

The product of its digits is 3840, while the sum is 30.

The square root of 21388512 is about 4624.7715619261. The cubic root of 21388512 is about 277.5834210686.

The spelling of 21388512 in words is "twenty-one million, three hundred eighty-eight thousand, five hundred twelve".