21504061728 has 54 divisors (see below), whose sum is σ = 61159253337. Its totient is φ = 7167191040.

The previous prime is 21504061697. The next prime is 21504061729. The reversal of 21504061728 is 82716040512.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

21504061728 is a `hidden beast` number, since 2 + 15 + 0 + 4 + 0 + 617 + 28 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 14287899024 + 7216162704 = 119532^2 + 84948^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=103692.

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

It is a junction number, because it is equal to n+sod(n) for n = 21504061692 and 21504061701.

It is not an unprimeable number, because it can be changed into a prime (21504061729) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 2484288 + ... + 2492928.

Almost surely, 2^21504061728 is an apocalyptic number.

It is an amenable number.

21504061728 is an abundant number, since it is smaller than the sum of its proper divisors (39655191609).

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

21504061728 is an frugal number, since it uses more digits than its factorization.

21504061728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17298 (or 8646 counting only the distinct ones).

The product of its (nonzero) digits is 26880, while the sum is 36.

The spelling of 21504061728 in words is "twenty-one billion, five hundred four million, sixty-one thousand, seven hundred twenty-eight".