20809729 has 2 divisors, whose sum is σ = 20809730. Its totient is φ = 20809728.

The previous prime is 20809709. The next prime is 20809757. The reversal of 20809729 is 92790802.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20793600 + 16129 = 4560^2 + 127^2 .

It is a cyclic number.

It is not a de Polignac number, because 20809729 - 2²³ = 12421121 is a prime.

It is not a weakly prime, because it can be changed into another prime (20809709) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10404864 + 10404865.

It is an arithmetic number, because the mean of its divisors is an integer number (10404865).

Almost surely, 2^20809729 is an apocalyptic number.

It is an amenable number.

20809729 is a deficient number, since it is larger than the sum of its proper divisors (1).

20809729 is an equidigital number, since it uses as much as digits as its factorization.

20809729 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 18144, while the sum is 37.

The square root of 20809729 is about 4561.7681878850. The cubic root of 20809729 is about 275.0566450806.

The spelling of 20809729 in words is "twenty million, eight hundred nine thousand, seven hundred twenty-nine".