20684009 has 2 divisors, whose sum is σ = 20684010. Its totient is φ = 20684008.

The previous prime is 20683997. The next prime is 20684011. The reversal of 20684009 is 90048602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13897984 + 6786025 = 3728^2 + 2605^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20684009 is a prime.

Together with 20684011, 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 (20684029) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10342004 + 10342005.

It is an arithmetic number, because the mean of its divisors is an integer number (10342005).

Almost surely, 2^20684009 is an apocalyptic number.

It is an amenable number.

20684009 is a deficient number, since it is larger than the sum of its proper divisors (1).

20684009 is an equidigital number, since it uses as much as digits as its factorization.

20684009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3456, while the sum is 29.

The square root of 20684009 is about 4547.9675680462. The cubic root of 20684009 is about 274.5016163311.

The spelling of 20684009 in words is "twenty million, six hundred eighty-four thousand, nine".