19728805 has 4 divisors (see below), whose sum is σ = 23674572. Its totient is φ = 15783040.

The previous prime is 19728781. The next prime is 19728811. The reversal of 19728805 is 50882791.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 50882791 = 29 ⋅1754579.

It can be written as a sum of positive squares in 2 ways, for example, as 3090564 + 16638241 = 1758^2 + 4079^2 .

It is not a de Polignac number, because 19728805 - 2¹⁵ = 19696037 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1972876 + ... + 1972885.

It is an arithmetic number, because the mean of its divisors is an integer number (5918643).

Almost surely, 2^19728805 is an apocalyptic number.

It is an amenable number.

19728805 is a deficient number, since it is larger than the sum of its proper divisors (3945767).

19728805 is an equidigital number, since it uses as much as digits as its factorization.

19728805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3945766.

The product of its (nonzero) digits is 40320, while the sum is 40.

The square root of 19728805 is about 4441.7119447348. The cubic root of 19728805 is about 270.2092799012.

The spelling of 19728805 in words is "nineteen million, seven hundred twenty-eight thousand, eight hundred five".