21888640 has 64 divisors (see below), whose sum is σ = 54639360. Its totient is φ = 8369152.

The previous prime is 21888623. The next prime is 21888653. The reversal of 21888640 is 4688812.

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

It is a super-2 number, since 2×21888640² = 958225122099200, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21888640.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13977 + ... + 15463.

It is an arithmetic number, because the mean of its divisors is an integer number (853740).

Almost surely, 2^21888640 is an apocalyptic number.

21888640 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 21888640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27319680).

21888640 is an abundant number, since it is smaller than the sum of its proper divisors (32750720).

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

21888640 is a wasteful number, since it uses less digits than its factorization.

21888640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1529 (or 1517 counting only the distinct ones).

The product of its (nonzero) digits is 24576, while the sum is 37.

The square root of 21888640 is about 4678.5296835651. The cubic root of 21888640 is about 279.7303526508.

The spelling of 21888640 in words is "twenty-one million, eight hundred eighty-eight thousand, six hundred forty".