21068388 has 72 divisors (see below), whose sum is σ = 58889376. Its totient is φ = 6297600.

The previous prime is 21068357. The next prime is 21068417. The reversal of 21068388 is 88386012.

21068388 is a `hidden beast` number, since 210 + 68 + 388 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 32548 + ... + 33188.

It is an arithmetic number, because the mean of its divisors is an integer number (817908).

Almost surely, 2^21068388 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 21068388, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29444688).

21068388 is an abundant number, since it is smaller than the sum of its proper divisors (37820988).

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

21068388 is a wasteful number, since it uses less digits than its factorization.

21068388 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 745 (or 740 counting only the distinct ones).

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

The square root of 21068388 is about 4590.0313724418. The cubic root of 21068388 is about 276.1915809121.

The spelling of 21068388 in words is "twenty-one million, sixty-eight thousand, three hundred eighty-eight".