20684509 has 2 divisors, whose sum is σ = 20684510. Its totient is φ = 20684508.

The previous prime is 20684479. The next prime is 20684519. The reversal of 20684509 is 90548602.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20052484 + 632025 = 4478^2 + 795^2 .

It is a cyclic number.

It is not a de Polignac number, because 20684509 - 2⁹ = 20683997 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20684519) 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, 10342254 + 10342255.

It is an arithmetic number, because the mean of its divisors is an integer number (10342255).

Almost surely, 2^20684509 is an apocalyptic number.

It is an amenable number.

20684509 is a deficient number, since it is larger than the sum of its proper divisors (1).

20684509 is an equidigital number, since it uses as much as digits as its factorization.

20684509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 17280, while the sum is 34.

The square root of 20684509 is about 4548.0225373232. The cubic root of 20684509 is about 274.5038281799.

The spelling of 20684509 in words is "twenty million, six hundred eighty-four thousand, five hundred nine".