21387648 has 32 divisors (see below), whose sum is σ = 56811960. Its totient is φ = 7129088.

The previous prime is 21387643. The next prime is 21387661. The reversal of 21387648 is 84678312.

It is a tau number, because it is divible by the number of its divisors (32).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21387643) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27465 + ... + 28232.

Almost surely, 2^21387648 is an apocalyptic number.

It is an amenable number.

21387648 is an abundant number, since it is smaller than the sum of its proper divisors (35424312).

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

21387648 is an equidigital number, since it uses as much as digits as its factorization.

21387648 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55714 (or 55702 counting only the distinct ones).

The product of its digits is 64512, while the sum is 39.

The square root of 21387648 is about 4624.6781509636. The cubic root of 21387648 is about 277.5796833097.

The spelling of 21387648 in words is "twenty-one million, three hundred eighty-seven thousand, six hundred forty-eight".