21084864 has 56 divisors (see below), whose sum is σ = 56174640. Its totient is φ = 6979584.

The previous prime is 21084853. The next prime is 21084881. The reversal of 21084864 is 46848012.

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, 36772 + ... + 37340.

Almost surely, 2^21084864 is an apocalyptic number.

21084864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21084864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28087320).

21084864 is an abundant number, since it is smaller than the sum of its proper divisors (35089776).

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

21084864 is a wasteful number, since it uses less digits than its factorization.

21084864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 777 (or 767 counting only the distinct ones).

The product of its (nonzero) digits is 12288, while the sum is 33.

The square root of 21084864 is about 4591.8257806672. The cubic root of 21084864 is about 276.2635583662.

The spelling of 21084864 in words is "twenty-one million, eighty-four thousand, eight hundred sixty-four".