21640478688 has 72 divisors (see below), whose sum is σ = 61953255000. Its totient is φ = 7165065984.

The previous prime is 21640478647. The next prime is 21640478737. The reversal of 21640478688 is 88687404612.

21640478688 is a `hidden beast` number, since 2 + 164 + 0 + 478 + 6 + 8 + 8 = 666.

It is a tau number, because it is divible by the number of its divisors (72).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 209238 + ... + 295061.

It is an arithmetic number, because the mean of its divisors is an integer number (860461875).

Almost surely, 2^21640478688 is an apocalyptic number.

It is an amenable number.

21640478688 is an abundant number, since it is smaller than the sum of its proper divisors (40312776312).

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

21640478688 is a wasteful number, since it uses less digits than its factorization.

21640478688 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 504464 (or 504453 counting only the distinct ones).

The product of its (nonzero) digits is 4128768, while the sum is 54.

The spelling of 21640478688 in words is "twenty-one billion, six hundred forty million, four hundred seventy-eight thousand, six hundred eighty-eight".