21881646 has 12 divisors (see below), whose sum is σ = 47410272. Its totient is φ = 7293876.

The previous prime is 21881627. The next prime is 21881647. The reversal of 21881646 is 64618812.

21881646 is a `hidden beast` number, since 2 + 1 + 8 + 8 + 1 + 646 = 666.

It is a self number, because there is not a number n which added to its sum of digits gives 21881646.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21881647) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 607806 + ... + 607841.

It is an arithmetic number, because the mean of its divisors is an integer number (3950856).

Almost surely, 2^21881646 is an apocalyptic number.

21881646 is an abundant number, since it is smaller than the sum of its proper divisors (25528626).

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

21881646 is a wasteful number, since it uses less digits than its factorization.

21881646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1215655 (or 1215652 counting only the distinct ones).

The product of its digits is 18432, while the sum is 36.

The square root of 21881646 is about 4677.7821667966. The cubic root of 21881646 is about 279.7005557257.

The spelling of 21881646 in words is "twenty-one million, eight hundred eighty-one thousand, six hundred forty-six".