21686694624 has 384 divisors, whose sum is σ = 76045132800. Its totient is φ = 5881559040.

The previous prime is 21686694619. The next prime is 21686694647. The reversal of 21686694624 is 42649668612.

21686694624 is a `hidden beast` number, since 2 + 1 + 6 + 8 + 6 + 6 + 9 + 4 + 624 = 666.

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

It is a nude number because it is divisible by every one of its digits.

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 63 ways as a sum of consecutive naturals, for example, 10697899 + ... + 10699925.

It is an arithmetic number, because the mean of its divisors is an integer number (198034200).

Almost surely, 2^21686694624 is an apocalyptic number.

21686694624 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 21686694624, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38022566400).

21686694624 is an abundant number, since it is smaller than the sum of its proper divisors (54358438176).

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

21686694624 is a wasteful number, since it uses less digits than its factorization.

21686694624 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2143 (or 2129 counting only the distinct ones).

The product of its digits is 5971968, while the sum is 54.

The spelling of 21686694624 in words is "twenty-one billion, six hundred eighty-six million, six hundred ninety-four thousand, six hundred twenty-four".