21365808 has 40 divisors (see below), whose sum is σ = 57102000. Its totient is φ = 6875904.

The previous prime is 21365801. The next prime is 21365809. The reversal of 21365808 is 80856312.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21365801) 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, 6283 + ... + 9066.

It is an arithmetic number, because the mean of its divisors is an integer number (1427550).

Almost surely, 2^21365808 is an apocalyptic number.

It is an amenable number.

21365808 is an abundant number, since it is smaller than the sum of its proper divisors (35736192).

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

21365808 is a wasteful number, since it uses less digits than its factorization.

21365808 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15389 (or 15383 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 33.

The square root of 21365808 is about 4622.3163024614. The cubic root of 21365808 is about 277.4851676189.

The spelling of 21365808 in words is "twenty-one million, three hundred sixty-five thousand, eight hundred eight".