261181566 has 24 divisors (see below), whose sum is σ = 566223840. Its totient is φ = 87009696.

The previous prime is 261181561. The next prime is 261181567. The reversal of 261181566 is 665181162.

261181566 is a `hidden beast` number, since 2 + 6 + 11 + 81 + 566 = 666.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 261181566.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261181561) 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, 39850 + ... + 45938.

It is an arithmetic number, because the mean of its divisors is an integer number (23592660).

Almost surely, 2^261181566 is an apocalyptic number.

261181566 is an abundant number, since it is smaller than the sum of its proper divisors (305042274).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

261181566 is a wasteful number, since it uses less digits than its factorization.

261181566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8480 (or 8477 counting only the distinct ones).

The product of its digits is 17280, while the sum is 36.

The square root of 261181566 is about 16161.1127710935. The cubic root of 261181566 is about 639.2158087295.

The spelling of 261181566 in words is "two hundred sixty-one million, one hundred eighty-one thousand, five hundred sixty-six".