261661184091 has 6 divisors (see below), whose sum is σ = 377955043700. Its totient is φ = 174440789388.

The previous prime is 261661184063. The next prime is 261661184143. The reversal of 261661184091 is 190481166162.

261661184091 is a `hidden beast` number, since 26 + 1 + 6 + 611 + 8 + 4 + 0 + 9 + 1 = 666.

It is not a de Polignac number, because 261661184091 - 2²² = 261656989787 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261661184591) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 14536732441 + ... + 14536732458.

Almost surely, 2^261661184091 is an apocalyptic number.

261661184091 is a deficient number, since it is larger than the sum of its proper divisors (116293859609).

261661184091 is a wasteful number, since it uses less digits than its factorization.

261661184091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29073464905 (or 29073464902 counting only the distinct ones).

The product of its (nonzero) digits is 124416, while the sum is 45.

The spelling of 261661184091 in words is "two hundred sixty-one billion, six hundred sixty-one million, one hundred eighty-four thousand, ninety-one".