261313249649 has 2 divisors, whose sum is σ = 261313249650. Its totient is φ = 261313249648.

The previous prime is 261313249607. The next prime is 261313249679. The reversal of 261313249649 is 946942313162.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 207863046400 + 53450203249 = 455920^2 + 231193^2 .

It is a cyclic number.

It is not a de Polignac number, because 261313249649 - 2¹² = 261313245553 is a prime.

It is a super-2 number, since 2×261313249649² (a number of 24 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 261313249597 and 261313249606.

It is not a weakly prime, because it can be changed into another prime (261313249679) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130656624824 + 130656624825.

It is an arithmetic number, because the mean of its divisors is an integer number (130656624825).

Almost surely, 2^261313249649 is an apocalyptic number.

It is an amenable number.

261313249649 is a deficient number, since it is larger than the sum of its proper divisors (1).

261313249649 is an equidigital number, since it uses as much as digits as its factorization.

261313249649 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1679616, while the sum is 50.

The spelling of 261313249649 in words is "two hundred sixty-one billion, three hundred thirteen million, two hundred forty-nine thousand, six hundred forty-nine".