20728009 has 2 divisors, whose sum is σ = 20728010. Its totient is φ = 20728008.

The previous prime is 20727989. The next prime is 20728033. The reversal of 20728009 is 90082702.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13286025 + 7441984 = 3645^2 + 2728^2 .

It is a cyclic number.

It is not a de Polignac number, because 20728009 - 2¹¹ = 20725961 is a prime.

It is not a weakly prime, because it can be changed into another prime (20728079) by changing a digit.

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 as a sum of consecutive naturals, namely, 10364004 + 10364005.

It is an arithmetic number, because the mean of its divisors is an integer number (10364005).

Almost surely, 2^20728009 is an apocalyptic number.

It is an amenable number.

20728009 is a deficient number, since it is larger than the sum of its proper divisors (1).

20728009 is an equidigital number, since it uses as much as digits as its factorization.

20728009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2016, while the sum is 28.

The square root of 20728009 is about 4552.8023238441. The cubic root of 20728009 is about 274.6961227390.

The spelling of 20728009 in words is "twenty million, seven hundred twenty-eight thousand, nine".