21865128 has 32 divisors (see below), whose sum is σ = 57879360. Its totient is φ = 6859520.

The previous prime is 21865121. The next prime is 21865133. The reversal of 21865128 is 82156812.

It is not an unprimeable number, because it can be changed into a prime (21865121) 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, 26388 + ... + 27203.

It is an arithmetic number, because the mean of its divisors is an integer number (1808730).

Almost surely, 2^21865128 is an apocalyptic number.

It is an amenable number.

21865128 is an abundant number, since it is smaller than the sum of its proper divisors (36014232).

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

21865128 is a wasteful number, since it uses less digits than its factorization.

21865128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 53617 (or 53613 counting only the distinct ones).

The product of its digits is 7680, while the sum is 33.

The square root of 21865128 is about 4676.0162531796. The cubic root of 21865128 is about 279.6301579624.

The spelling of 21865128 in words is "twenty-one million, eight hundred sixty-five thousand, one hundred twenty-eight".