21257646816 has 96 divisors (see below), whose sum is σ = 65972067840. Its totient is φ = 5864173056.

The previous prime is 21257646811. The next prime is 21257646827. The reversal of 21257646816 is 61864675212.

It is a tau number, because it is divible by the number of its divisors (96).

It is a hoax number, since the sum of its digits (48) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21257646811) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 525916 + ... + 564891.

It is an arithmetic number, because the mean of its divisors is an integer number (687209040).

Almost surely, 2^21257646816 is an apocalyptic number.

It is an amenable number.

21257646816 is an abundant number, since it is smaller than the sum of its proper divisors (44714421024).

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

21257646816 is a wasteful number, since it uses less digits than its factorization.

21257646816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1090856 (or 1090848 counting only the distinct ones).

The product of its digits is 967680, while the sum is 48.

The spelling of 21257646816 in words is "twenty-one billion, two hundred fifty-seven million, six hundred forty-six thousand, eight hundred sixteen".