21659808 has 48 divisors (see below), whose sum is σ = 58254336. Its totient is φ = 7042560.

The previous prime is 21659801. The next prime is 21659843. The reversal of 21659808 is 80895612.

It is a tau number, because it is divible by the number of its divisors (48).

It is not an unprimeable number, because it can be changed into a prime (21659801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1185 + ... + 6687.

It is an arithmetic number, because the mean of its divisors is an integer number (1213632).

Almost surely, 2^21659808 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 21659808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29127168).

21659808 is an abundant number, since it is smaller than the sum of its proper divisors (36594528).

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

21659808 is a wasteful number, since it uses less digits than its factorization.

21659808 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5557 (or 5549 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 39.

The square root of 21659808 is about 4654.0098839603. The cubic root of 21659808 is about 278.7521340168.

The spelling of 21659808 in words is "twenty-one million, six hundred fifty-nine thousand, eight hundred eight".