261665573346557 has 8 divisors (see below), whose sum is σ = 265099099099896. Its totient is φ = 258254128145152.

The previous prime is 261665573346547. The next prime is 261665573346577. The reversal of 261665573346557 is 755643375566162.

It can be written as a sum of positive squares in 4 ways, for example, as 41389484773156 + 220276088573401 = 6433466^2 + 14841701^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 261665573346557 - 2⁶ = 261665573346493 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261665573346547) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (31) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5520114128 + ... + 5520161529.

It is an arithmetic number, because the mean of its divisors is an integer number (33137387387487).

Almost surely, 2^{261665573346557} is an apocalyptic number.

It is an amenable number.

261665573346557 is a deficient number, since it is larger than the sum of its proper divisors (3433525753339).

261665573346557 is a wasteful number, since it uses less digits than its factorization.

261665573346557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11040275967.

The product of its digits is 2857680000, while the sum is 71.

The spelling of 261665573346557 in words is "two hundred sixty-one trillion, six hundred sixty-five billion, five hundred seventy-three million, three hundred forty-six thousand, five hundred fifty-seven".