20728189 has 4 divisors (see below), whose sum is σ = 20961180. Its totient is φ = 20495200.

The previous prime is 20728159. The next prime is 20728199. The reversal of 20728189 is 98182702.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2152089 + 18576100 = 1467^2 + 4310^2 .

It is a cyclic number.

It is not a de Polignac number, because 20728189 - 2⁷ = 20728061 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20728109) 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, 116362 + ... + 116539.

It is an arithmetic number, because the mean of its divisors is an integer number (5240295).

Almost surely, 2^20728189 is an apocalyptic number.

It is an amenable number.

20728189 is a deficient number, since it is larger than the sum of its proper divisors (232991).

20728189 is an equidigital number, since it uses as much as digits as its factorization.

20728189 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 232990.

The product of its (nonzero) digits is 16128, while the sum is 37.

The square root of 20728189 is about 4552.8220918459. The cubic root of 20728189 is about 274.6969178815.

The spelling of 20728189 in words is "twenty million, seven hundred twenty-eight thousand, one hundred eighty-nine".