20557728 has 72 divisors (see below), whose sum is σ = 59921316. Its totient is φ = 6681600.

The previous prime is 20557721. The next prime is 20557729. The reversal of 20557728 is 82775502.

It can be written as a sum of positive squares in 2 ways, for example, as 12873744 + 7683984 = 3588^2 + 2772^2 .

It is a tau number, because it is divible by the number of its divisors (72).

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 = 20557692 and 20557701.

It is not an unprimeable number, because it can be changed into a prime (20557721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10938 + ... + 12678.

Almost surely, 2^20557728 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 20557728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29960658).

20557728 is an abundant number, since it is smaller than the sum of its proper divisors (39363588).

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

20557728 is a wasteful number, since it uses less digits than its factorization.

20557728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1798 (or 1787 counting only the distinct ones).

The product of its (nonzero) digits is 39200, while the sum is 36.

The square root of 20557728 is about 4534.0630785202. The cubic root of 20557728 is about 273.9418421329.

The spelling of 20557728 in words is "twenty million, five hundred fifty-seven thousand, seven hundred twenty-eight".