261664242857 has 2 divisors, whose sum is σ = 261664242858. Its totient is φ = 261664242856.

The previous prime is 261664242839. The next prime is 261664242901. The reversal of 261664242857 is 758242466162.

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., 225343887616 + 36320355241 = 474704^2 + 190579^2 .

It is a cyclic number.

It is not a de Polignac number, because 261664242857 - 2⁶ = 261664242793 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 261664242799 and 261664242808.

It is not a weakly prime, because it can be changed into another prime (261664242457) 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, 130832121428 + 130832121429.

It is an arithmetic number, because the mean of its divisors is an integer number (130832121429).

Almost surely, 2^261664242857 is an apocalyptic number.

It is an amenable number.

261664242857 is a deficient number, since it is larger than the sum of its proper divisors (1).

261664242857 is an equidigital number, since it uses as much as digits as its factorization.

261664242857 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7741440, while the sum is 53.

The spelling of 261664242857 in words is "two hundred sixty-one billion, six hundred sixty-four million, two hundred forty-two thousand, eight hundred fifty-seven".