21581309968 has 20 divisors (see below), whose sum is σ = 42437876560. Its totient is φ = 10629599904.

The previous prime is 21581309909. The next prime is 21581309977. The reversal of 21581309968 is 86990318512.

It is a super-2 number, since 2×21581309968² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 10064838 + ... + 10066981.

It is an arithmetic number, because the mean of its divisors is an integer number (2121893828).

Almost surely, 2^21581309968 is an apocalyptic number.

It is an amenable number.

21581309968 is a deficient number, since it is larger than the sum of its proper divisors (20856566592).

21581309968 is a wasteful number, since it uses less digits than its factorization.

21581309968 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20131894 (or 20131888 counting only the distinct ones).

The product of its (nonzero) digits is 933120, while the sum is 52.

The spelling of 21581309968 in words is "twenty-one billion, five hundred eighty-one million, three hundred nine thousand, nine hundred sixty-eight".