21365971808 has 48 divisors (see below), whose sum is σ = 46203333120. Its totient is φ = 9680685696.

The previous prime is 21365971799. The next prime is 21365971843. The reversal of 21365971808 is 80817956312.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 749960 + ... + 777927.

It is an arithmetic number, because the mean of its divisors is an integer number (962569440).

Almost surely, 2^21365971808 is an apocalyptic number.

It is an amenable number.

21365971808 is an abundant number, since it is smaller than the sum of its proper divisors (24837361312).

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

21365971808 is a wasteful number, since it uses less digits than its factorization.

21365971808 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1527939 (or 1527931 counting only the distinct ones).

The product of its (nonzero) digits is 725760, while the sum is 50.

The spelling of 21365971808 in words is "twenty-one billion, three hundred sixty-five million, nine hundred seventy-one thousand, eight hundred eight".