20728849 has 4 divisors (see below), whose sum is σ = 20809764. Its totient is φ = 20647936.

The previous prime is 20728847. The next prime is 20728859. The reversal of 20728849 is 94882702.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 94882702 = 2 ⋅47441351.

It can be written as a sum of positive squares in 2 ways, for example, as 20638849 + 90000 = 4543^2 + 300^2 .

It is a cyclic number.

It is not a de Polignac number, because 20728849 - 2¹ = 20728847 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 not an unprimeable number, because it can be changed into a prime (20728847) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 40072 + ... + 40585.

It is an arithmetic number, because the mean of its divisors is an integer number (5202441).

Almost surely, 2^20728849 is an apocalyptic number.

It is an amenable number.

20728849 is a deficient number, since it is larger than the sum of its proper divisors (80915).

20728849 is an equidigital number, since it uses as much as digits as its factorization.

20728849 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80914.

The product of its (nonzero) digits is 64512, while the sum is 40.

The square root of 20728849 is about 4552.8945737849. The cubic root of 20728849 is about 274.6998333644.

The spelling of 20728849 in words is "twenty million, seven hundred twenty-eight thousand, eight hundred forty-nine".