20729909 has 2 divisors, whose sum is σ = 20729910. Its totient is φ = 20729908.

The previous prime is 20729903. The next prime is 20729927. The reversal of 20729909 is 90992702.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20729809 + 100 = 4553^2 + 10^2 .

It is a cyclic number.

It is not a de Polignac number, because 20729909 - 2¹² = 20725813 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20729903) 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, 10364954 + 10364955.

It is an arithmetic number, because the mean of its divisors is an integer number (10364955).

Almost surely, 2^20729909 is an apocalyptic number.

It is an amenable number.

20729909 is a deficient number, since it is larger than the sum of its proper divisors (1).

20729909 is an equidigital number, since it uses as much as digits as its factorization.

20729909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20412, while the sum is 38.

The square root of 20729909 is about 4553.0109817570. The cubic root of 20729909 is about 274.7045156771.

The spelling of 20729909 in words is "twenty million, seven hundred twenty-nine thousand, nine hundred nine".