21905688 has 64 divisors (see below), whose sum is σ = 63256320. Its totient is φ = 6192000.

The previous prime is 21905687. The next prime is 21905699. The reversal of 21905688 is 88650912.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21905687) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16323 + ... + 17613.

It is an arithmetic number, because the mean of its divisors is an integer number (988380).

Almost surely, 2^21905688 is an apocalyptic number.

21905688 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21905688, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31628160).

21905688 is an abundant number, since it is smaller than the sum of its proper divisors (41350632).

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

21905688 is a wasteful number, since it uses less digits than its factorization.

21905688 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1408 (or 1404 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 39.

The square root of 21905688 is about 4680.3512688686. The cubic root of 21905688 is about 279.8029566060.

The spelling of 21905688 in words is "twenty-one million, nine hundred five thousand, six hundred eighty-eight".