21681392 has 40 divisors (see below), whose sum is σ = 45086400. Its totient is φ = 10063872.

The previous prime is 21681389. The next prime is 21681421. The reversal of 21681392 is 29318612.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20984 + ... + 21992.

It is an arithmetic number, because the mean of its divisors is an integer number (1127160).

Almost surely, 2^21681392 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 21681392, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22543200).

21681392 is an abundant number, since it is smaller than the sum of its proper divisors (23405008).

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

21681392 is a wasteful number, since it uses less digits than its factorization.

21681392 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1113 (or 1107 counting only the distinct ones).

The product of its digits is 5184, while the sum is 32.

The square root of 21681392 is about 4656.3281671291. The cubic root of 21681392 is about 278.8446954506.

The spelling of 21681392 in words is "twenty-one million, six hundred eighty-one thousand, three hundred ninety-two".