21688042464 has 384 divisors, whose sum is σ = 73574645760. Its totient is φ = 6149721600.

The previous prime is 21688042429. The next prime is 21688042471. The reversal of 21688042464 is 46424088612.

21688042464 is a `hidden beast` number, since 2 + 168 + 8 + 0 + 424 + 64 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 10272769 + ... + 10274879.

It is an arithmetic number, because the mean of its divisors is an integer number (191600640).

Almost surely, 2^21688042464 is an apocalyptic number.

21688042464 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21688042464, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36787322880).

21688042464 is an abundant number, since it is smaller than the sum of its proper divisors (51886603296).

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

21688042464 is a wasteful number, since it uses less digits than its factorization.

21688042464 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2211 (or 2197 counting only the distinct ones).

The product of its (nonzero) digits is 589824, while the sum is 45.

The spelling of 21688042464 in words is "twenty-one billion, six hundred eighty-eight million, forty-two thousand, four hundred sixty-four".