21039072 has 48 divisors (see below), whose sum is σ = 56068992. Its totient is φ = 6906240.

The previous prime is 21039001. The next prime is 21039079. The reversal of 21039072 is 27093012.

It is a tau number, because it is divible by the number of its divisors (48).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21039079) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4797 + ... + 8067.

It is an arithmetic number, because the mean of its divisors is an integer number (1168104).

Almost surely, 2^21039072 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 21039072, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28034496).

21039072 is an abundant number, since it is smaller than the sum of its proper divisors (35029920).

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

21039072 is a wasteful number, since it uses less digits than its factorization.

21039072 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3351 (or 3343 counting only the distinct ones).

The product of its (nonzero) digits is 756, while the sum is 24.

The square root of 21039072 is about 4586.8368185494. The cubic root of 21039072 is about 276.0634174793.

It can be divided in two parts, 2103 and 9072, that added together give a triangular number (11175 = T₁₄₉).

The spelling of 21039072 in words is "twenty-one million, thirty-nine thousand, seventy-two".