261155245561 has 12 divisors (see below), whose sum is σ = 304478624592. Its totient is φ = 223342036008.

The previous prime is 261155245511. The next prime is 261155245627. The reversal of 261155245561 is 165542551162.

It is not a de Polignac number, because 261155245561 - 2¹⁷ = 261155114489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261155245501) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5993755 + ... + 6037168.

It is an arithmetic number, because the mean of its divisors is an integer number (25373218716).

Almost surely, 2^261155245561 is an apocalyptic number.

It is an amenable number.

261155245561 is a deficient number, since it is larger than the sum of its proper divisors (43323379031).

261155245561 is a wasteful number, since it uses less digits than its factorization.

261155245561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12031380 (or 12031373 counting only the distinct ones).

The product of its digits is 360000, while the sum is 43.

The spelling of 261155245561 in words is "two hundred sixty-one billion, one hundred fifty-five million, two hundred forty-five thousand, five hundred sixty-one".