21043968 has 144 divisors (see below), whose sum is σ = 63576576. Its totient is φ = 6123520.

The previous prime is 21043949. The next prime is 21043973. The reversal of 21043968 is 86934012.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 397030 + ... + 397082.

It is an arithmetic number, because the mean of its divisors is an integer number (441504).

Almost surely, 2^21043968 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 21043968, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31788288).

21043968 is an abundant number, since it is smaller than the sum of its proper divisors (42532608).

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

21043968 is a wasteful number, since it uses less digits than its factorization.

21043968 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 130 (or 116 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 33.

The square root of 21043968 is about 4587.3704886351. The cubic root of 21043968 is about 276.0848300470.

The spelling of 21043968 in words is "twenty-one million, forty-three thousand, nine hundred sixty-eight".