261631161 has 48 divisors (see below), whose sum is σ = 434367360. Its totient is φ = 155469600.

The previous prime is 261631151. The next prime is 261631163. The reversal of 261631161 is 161136162.

261631161 is a `hidden beast` number, since 2 + 616 + 31 + 16 + 1 = 666.

It is not a de Polignac number, because 261631161 - 2¹⁰ = 261630137 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (261631163) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 172396 + ... + 173906.

It is an arithmetic number, because the mean of its divisors is an integer number (9049320).

Almost surely, 2^261631161 is an apocalyptic number.

It is an amenable number.

261631161 is a deficient number, since it is larger than the sum of its proper divisors (172736199).

261631161 is a wasteful number, since it uses less digits than its factorization.

261631161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1595 (or 1578 counting only the distinct ones).

The product of its digits is 1296, while the sum is 27.

The square root of 261631161 is about 16175.0165687705. The cubic root of 261631161 is about 639.5823781001.

The spelling of 261631161 in words is "two hundred sixty-one million, six hundred thirty-one thousand, one hundred sixty-one".