20409689 has 2 divisors, whose sum is σ = 20409690. Its totient is φ = 20409688.

The previous prime is 20409679. The next prime is 20409691. The reversal of 20409689 is 98690402.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20403289 + 6400 = 4517^2 + 80^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20409689 is a prime.

Together with 20409691, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20409679) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10204844 + 10204845.

It is an arithmetic number, because the mean of its divisors is an integer number (10204845).

Almost surely, 2^20409689 is an apocalyptic number.

It is an amenable number.

20409689 is a deficient number, since it is larger than the sum of its proper divisors (1).

20409689 is an equidigital number, since it uses as much as digits as its factorization.

20409689 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 31104, while the sum is 38.

The square root of 20409689 is about 4517.7083792560. The cubic root of 20409689 is about 273.2826932096.

The spelling of 20409689 in words is "twenty million, four hundred nine thousand, six hundred eighty-nine".