21808864 has 96 divisors (see below), whose sum is σ = 54867456. Its totient is φ = 8286720.

The previous prime is 21808861. The next prime is 21808867. The reversal of 21808864 is 46880812.

It is an interprime number because it is at equal distance from previous prime (21808861) and next prime (21808867).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21808861) 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 15 ways as a sum of consecutive naturals, for example, 130509 + ... + 130675.

It is an arithmetic number, because the mean of its divisors is an integer number (571536).

Almost surely, 2^21808864 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 21808864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27433728).

21808864 is an abundant number, since it is smaller than the sum of its proper divisors (33058592).

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

21808864 is a wasteful number, since it uses less digits than its factorization.

21808864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 248 (or 240 counting only the distinct ones).

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

The square root of 21808864 is about 4669.9961456087. The cubic root of 21808864 is about 279.3901010477.

The spelling of 21808864 in words is "twenty-one million, eight hundred eight thousand, eight hundred sixty-four".