261636165 has 24 divisors (see below), whose sum is σ = 518289408. Its totient is φ = 119604960.

The previous prime is 261636091. The next prime is 261636181. The reversal of 261636165 is 561636162.

261636165 is a `hidden beast` number, since 2 + 6 + 1 + 636 + 16 + 5 = 666.

It is not a de Polignac number, because 261636165 - 2⁹ = 261635653 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 414981 + ... + 415610.

It is an arithmetic number, because the mean of its divisors is an integer number (21595392).

Almost surely, 2^261636165 is an apocalyptic number.

It is an amenable number.

261636165 is a deficient number, since it is larger than the sum of its proper divisors (256653243).

261636165 is a wasteful number, since it uses less digits than its factorization.

261636165 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 830609 (or 830606 counting only the distinct ones).

The product of its digits is 38880, while the sum is 36.

The square root of 261636165 is about 16175.1712510254. The cubic root of 261636165 is about 639.5864556595.

It can be divided in two parts, 2616 and 36165, that added together give a triangular number (38781 = T₂₇₈).

The spelling of 261636165 in words is "two hundred sixty-one million, six hundred thirty-six thousand, one hundred sixty-five".