21105688 has 32 divisors (see below), whose sum is σ = 41067360. Its totient is φ = 10160640.

The previous prime is 21105683. The next prime is 21105703. The reversal of 21105688 is 88650112.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21105683) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 33133 + ... + 33763.

It is an arithmetic number, because the mean of its divisors is an integer number (1283355).

Almost surely, 2^21105688 is an apocalyptic number.

It is an amenable number.

21105688 is a deficient number, since it is larger than the sum of its proper divisors (19961672).

21105688 is a wasteful number, since it uses less digits than its factorization.

21105688 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 787 (or 783 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 31.

The square root of 21105688 is about 4594.0927287115. The cubic root of 21105688 is about 276.3544769744.

The spelling of 21105688 in words is "twenty-one million, one hundred five thousand, six hundred eighty-eight".