21686144 has 64 divisors (see below), whose sum is σ = 46899600. Its totient is φ = 9953280.

The previous prime is 21686123. The next prime is 21686177. The reversal of 21686144 is 44168612.

It is a tau number, because it is divible by the number of its divisors (64).

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a self number, because there is not a number n which added to its sum of digits gives 21686144.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 89864 + ... + 90104.

Almost surely, 2^21686144 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 21686144, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23449800).

21686144 is an abundant number, since it is smaller than the sum of its proper divisors (25213456).

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

21686144 is a wasteful number, since it uses less digits than its factorization.

21686144 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 311 (or 299 counting only the distinct ones).

The product of its digits is 9216, while the sum is 32.

The square root of 21686144 is about 4656.8384124854. The cubic root of 21686144 is about 278.8650658094.

The spelling of 21686144 in words is "twenty-one million, six hundred eighty-six thousand, one hundred forty-four".