21157694656 has 28 divisors (see below), whose sum is σ = 47982629968. Its totient is φ = 9067583232.

The previous prime is 21157694651. The next prime is 21157694659. The reversal of 21157694656 is 65649675112.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (28).

It is not an unprimeable number, because it can be changed into a prime (21157694651) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23613051 + ... + 23613946.

It is an arithmetic number, because the mean of its divisors is an integer number (1713665356).

Almost surely, 2^21157694656 is an apocalyptic number.

It is an amenable number.

21157694656 is an abundant number, since it is smaller than the sum of its proper divisors (26824935312).

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

21157694656 is an equidigital number, since it uses as much as digits as its factorization.

21157694656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47227016 (or 47227006 counting only the distinct ones).

The product of its digits is 2721600, while the sum is 52.

The spelling of 21157694656 in words is "twenty-one billion, one hundred fifty-seven million, six hundred ninety-four thousand, six hundred fifty-six".