20705809 has 2 divisors, whose sum is σ = 20705810. Its totient is φ = 20705808.

The previous prime is 20705791. The next prime is 20705827. The reversal of 20705809 is 90850702.

It is a balanced prime because it is at equal distance from previous prime (20705791) and next prime (20705827).

It can be written as a sum of positive squares in only one way, i.e., 16785409 + 3920400 = 4097^2 + 1980^2 .

It is a cyclic number.

It is not a de Polignac number, because 20705809 - 2⁵ = 20705777 is a prime.

It is not a weakly prime, because it can be changed into another prime (20705849) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10352904 + 10352905.

It is an arithmetic number, because the mean of its divisors is an integer number (10352905).

Almost surely, 2^20705809 is an apocalyptic number.

It is an amenable number.

20705809 is a deficient number, since it is larger than the sum of its proper divisors (1).

20705809 is an equidigital number, since it uses as much as digits as its factorization.

20705809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5040, while the sum is 31.

The square root of 20705809 is about 4550.3636118447. The cubic root of 20705809 is about 274.5980198560.

The spelling of 20705809 in words is "twenty million, seven hundred five thousand, eight hundred nine".