21656384478 has 32 divisors (see below), whose sum is σ = 48374676000. Its totient is φ = 7181388288.

The previous prime is 21656384437. The next prime is 21656384479. The reversal of 21656384478 is 87448365612.

It is a happy number.

21656384478 is a `hidden beast` number, since 2 + 1 + 6 + 563 + 8 + 4 + 4 + 78 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21656384479) 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, 1028553 + ... + 1049396.

It is an arithmetic number, because the mean of its divisors is an integer number (1511708625).

Almost surely, 2^21656384478 is an apocalyptic number.

21656384478 is an abundant number, since it is smaller than the sum of its proper divisors (26718291522).

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

21656384478 is a wasteful number, since it uses less digits than its factorization.

21656384478 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2078153 (or 2078147 counting only the distinct ones).

The product of its digits is 7741440, while the sum is 54.

The spelling of 21656384478 in words is "twenty-one billion, six hundred fifty-six million, three hundred eighty-four thousand, four hundred seventy-eight".