21088640 has 64 divisors (see below), whose sum is σ = 51150960. Its totient is φ = 8312832.

The previous prime is 21088621. The next prime is 21088667. The reversal of 21088640 is 4688012.

It is a tau number, because it is divible by the number of its divisors (64).

It is a congruent number.

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, 52922 + ... + 53318.

Almost surely, 2^21088640 is an apocalyptic number.

21088640 is a gapful number since it is divisible by the number (20) 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 21088640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25575480).

21088640 is an abundant number, since it is smaller than the sum of its proper divisors (30062320).

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

21088640 is an equidigital number, since it uses as much as digits as its factorization.

21088640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 499 (or 487 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 29.

The square root of 21088640 is about 4592.2369276857. The cubic root of 21088640 is about 276.2800490098.

The spelling of 21088640 in words is "twenty-one million, eighty-eight thousand, six hundred forty".