20684309 has 2 divisors, whose sum is σ = 20684310. Its totient is φ = 20684308.

The previous prime is 20684281. The next prime is 20684317. The reversal of 20684309 is 90348602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18464209 + 2220100 = 4297^2 + 1490^2 .

It is a cyclic number.

It is not a de Polignac number, because 20684309 - 2¹² = 20680213 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 (20684009) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10342154 + 10342155.

It is an arithmetic number, because the mean of its divisors is an integer number (10342155).

Almost surely, 2^20684309 is an apocalyptic number.

It is an amenable number.

20684309 is a deficient number, since it is larger than the sum of its proper divisors (1).

20684309 is an equidigital number, since it uses as much as digits as its factorization.

20684309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10368, while the sum is 32.

The square root of 20684309 is about 4548.0005496921. Note that the first 3 decimals coincide. The cubic root of 20684309 is about 274.5029434446.

The spelling of 20684309 in words is "twenty million, six hundred eighty-four thousand, three hundred nine".