20561212849 has 2 divisors, whose sum is σ = 20561212850. Its totient is φ = 20561212848.

The previous prime is 20561212829. The next prime is 20561212873. The reversal of 20561212849 is 94821216502.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20109225249 + 451987600 = 141807^2 + 21260^2 .

It is a cyclic number.

It is not a de Polignac number, because 20561212849 - 2⁹ = 20561212337 is a prime.

It is not a weakly prime, because it can be changed into another prime (20561212829) 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, 10280606424 + 10280606425.

It is an arithmetic number, because the mean of its divisors is an integer number (10280606425).

Almost surely, 2^20561212849 is an apocalyptic number.

It is an amenable number.

20561212849 is a deficient number, since it is larger than the sum of its proper divisors (1).

20561212849 is an equidigital number, since it uses as much as digits as its factorization.

20561212849 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 69120, while the sum is 40.

The spelling of 20561212849 in words is "twenty billion, five hundred sixty-one million, two hundred twelve thousand, eight hundred forty-nine".