21284864 has 48 divisors (see below), whose sum is σ = 44881200. Its totient is φ = 10063872.

The previous prime is 21284839. The next prime is 21284903. The reversal of 21284864 is 46848212.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 38639 + ... + 39185.

It is an arithmetic number, because the mean of its divisors is an integer number (935025).

Almost surely, 2^21284864 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 21284864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22440600).

21284864 is an abundant number, since it is smaller than the sum of its proper divisors (23596336).

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

21284864 is an equidigital number, since it uses as much as digits as its factorization.

21284864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 588 (or 568 counting only the distinct ones).

The product of its digits is 24576, while the sum is 35.

The square root of 21284864 is about 4613.5522106074. The cubic root of 21284864 is about 277.1343082251.

The spelling of 21284864 in words is "twenty-one million, two hundred eighty-four thousand, eight hundred sixty-four".