21688884 has 120 divisors (see below), whose sum is σ = 66187968. Its totient is φ = 6065280.

The previous prime is 21688883. The next prime is 21688903. The reversal of 21688884 is 48888612.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21688883) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 165499 + ... + 165629.

Almost surely, 2^21688884 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 21688884, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33093984).

21688884 is an abundant number, since it is smaller than the sum of its proper divisors (44499084).

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

21688884 is a wasteful number, since it uses less digits than its factorization.

21688884 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 227 (or 216 counting only the distinct ones).

The product of its digits is 196608, while the sum is 45.

The square root of 21688884 is about 4657.1325942043. The cubic root of 21688884 is about 278.8768099919.

The spelling of 21688884 in words is "twenty-one million, six hundred eighty-eight thousand, eight hundred eighty-four".