21089656568 has 8 divisors (see below), whose sum is σ = 39543106080. Its totient is φ = 10544828280.

The previous prime is 21089656519. The next prime is 21089656583. The reversal of 21089656568 is 86565698012.

It is a tau number, because it is divible by the number of its divisors (8).

It is a super-2 number, since 2×21089656568² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1318103528 + ... + 1318103543.

It is an arithmetic number, because the mean of its divisors is an integer number (4942888260).

Almost surely, 2^21089656568 is an apocalyptic number.

It is an amenable number.

21089656568 is a deficient number, since it is larger than the sum of its proper divisors (18453449512).

21089656568 is a wasteful number, since it uses less digits than its factorization.

21089656568 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2636207077 (or 2636207073 counting only the distinct ones).

The product of its (nonzero) digits is 6220800, while the sum is 56.

The spelling of 21089656568 in words is "twenty-one billion, eighty-nine million, six hundred fifty-six thousand, five hundred sixty-eight".