21686976 has 84 divisors (see below), whose sum is σ = 64904112. Its totient is φ = 6910464.

The previous prime is 21686971. The next prime is 21686989. The reversal of 21686976 is 67968612.

It is not an unprimeable number, because it can be changed into a prime (21686971) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 12430 + ... + 14066.

It is an arithmetic number, because the mean of its divisors is an integer number (772668).

Almost surely, 2^21686976 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 21686976, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32452056).

21686976 is an abundant number, since it is smaller than the sum of its proper divisors (43217136).

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

21686976 is a wasteful number, since it uses less digits than its factorization.

21686976 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1678 (or 1665 counting only the distinct ones).

The product of its digits is 217728, while the sum is 45.

The square root of 21686976 is about 4656.9277426217. The cubic root of 21686976 is about 278.8686320307.

The spelling of 21686976 in words is "twenty-one million, six hundred eighty-six thousand, nine hundred seventy-six".