21061728 has 96 divisors (see below), whose sum is σ = 64713600. Its totient is φ = 6645888.

The previous prime is 21061717. The next prime is 21061739. The reversal of 21061728 is 82716012.

21061728 is a `hidden beast` number, since 21 + 0 + 617 + 28 = 666.

It is an interprime number because it is at equal distance from previous prime (21061717) and next prime (21061739).

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

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, 15775 + ... + 17057.

It is an arithmetic number, because the mean of its divisors is an integer number (674100).

Almost surely, 2^21061728 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 21061728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32356800).

21061728 is an abundant number, since it is smaller than the sum of its proper divisors (43651872).

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

21061728 is a wasteful number, since it uses less digits than its factorization.

21061728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1321 (or 1307 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 21061728 is about 4589.3058298614. The cubic root of 21061728 is about 276.1624752241.

The spelling of 21061728 in words is "twenty-one million, sixty-one thousand, seven hundred twenty-eight".