21685564416 has 176 divisors, whose sum is σ = 60658800128. Its totient is φ = 6878822400.

The previous prime is 21685564273. The next prime is 21685564423. The reversal of 21685564416 is 61446558612.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5807286 + ... + 5811018.

Almost surely, 2^21685564416 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21685564416, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30329400064).

21685564416 is an abundant number, since it is smaller than the sum of its proper divisors (38973235712).

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

21685564416 is a wasteful number, since it uses less digits than its factorization.

21685564416 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3848 (or 3830 counting only the distinct ones).

The product of its digits is 1382400, while the sum is 48.

The spelling of 21685564416 in words is "twenty-one billion, six hundred eighty-five million, five hundred sixty-four thousand, four hundred sixteen".