20408309 has 2 divisors, whose sum is σ = 20408310. Its totient is φ = 20408308.

The previous prime is 20408303. The next prime is 20408341. The reversal of 20408309 is 90380402.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15132100 + 5276209 = 3890^2 + 2297^2 .

It is a cyclic number.

It is not a de Polignac number, because 20408309 - 2¹² = 20404213 is a prime.

It is a Sophie Germain 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 (20408303) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10204154 + 10204155.

It is an arithmetic number, because the mean of its divisors is an integer number (10204155).

Almost surely, 2^20408309 is an apocalyptic number.

It is an amenable number.

20408309 is a deficient number, since it is larger than the sum of its proper divisors (1).

20408309 is an equidigital number, since it uses as much as digits as its factorization.

20408309 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1728, while the sum is 26.

The square root of 20408309 is about 4517.5556443723. Note that the first 3 decimals coincide. The cubic root of 20408309 is about 273.2765337393.

The spelling of 20408309 in words is "twenty million, four hundred eight thousand, three hundred nine".