261664242901 has 2 divisors, whose sum is σ = 261664242902. Its totient is φ = 261664242900.

The previous prime is 261664242857. The next prime is 261664242919. The reversal of 261664242901 is 109242466162.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 260497952100 + 1166290801 = 510390^2 + 34151^2 .

It is a cyclic number.

It is not a de Polignac number, because 261664242901 - 2³⁷ = 124225289429 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261664242401) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130832121450 + 130832121451.

It is an arithmetic number, because the mean of its divisors is an integer number (130832121451).

Almost surely, 2^261664242901 is an apocalyptic number.

It is an amenable number.

261664242901 is a deficient number, since it is larger than the sum of its proper divisors (1).

261664242901 is an equidigital number, since it uses as much as digits as its factorization.

261664242901 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 248832, while the sum is 43.

The spelling of 261664242901 in words is "two hundred sixty-one billion, six hundred sixty-four million, two hundred forty-two thousand, nine hundred one".