261549952861 has 2 divisors, whose sum is σ = 261549952862. Its totient is φ = 261549952860.

The previous prime is 261549952847. The next prime is 261549952901. The reversal of 261549952861 is 168259945162.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 171193200025 + 90356752836 = 413755^2 + 300594^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261549952861 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 261549952796 and 261549952805.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261549952361) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130774976430 + 130774976431.

It is an arithmetic number, because the mean of its divisors is an integer number (130774976431).

Almost surely, 2^261549952861 is an apocalyptic number.

It is an amenable number.

261549952861 is a deficient number, since it is larger than the sum of its proper divisors (1).

261549952861 is an equidigital number, since it uses as much as digits as its factorization.

261549952861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9331200, while the sum is 58.

The spelling of 261549952861 in words is "two hundred sixty-one billion, five hundred forty-nine million, nine hundred fifty-two thousand, eight hundred sixty-one".