20845666409 has 2 divisors, whose sum is σ = 20845666410. Its totient is φ = 20845666408.

The previous prime is 20845666351. The next prime is 20845666417. The reversal of 20845666409 is 90466654802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20836056409 + 9610000 = 144347^2 + 3100^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20845666409 is a prime.

It is not a weakly prime, because it can be changed into another prime (20845666459) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10422833204 + 10422833205.

It is an arithmetic number, because the mean of its divisors is an integer number (10422833205).

Almost surely, 2^20845666409 is an apocalyptic number.

It is an amenable number.

20845666409 is a deficient number, since it is larger than the sum of its proper divisors (1).

20845666409 is an equidigital number, since it uses as much as digits as its factorization.

20845666409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2488320, while the sum is 50.

The spelling of 20845666409 in words is "twenty billion, eight hundred forty-five million, six hundred sixty-six thousand, four hundred nine".