261431661 has 16 divisors (see below), whose sum is σ = 369537984. Its totient is φ = 163832064.

The previous prime is 261431647. The next prime is 261431663. The reversal of 261431661 is 166134162.

It is not a de Polignac number, because 261431661 - 2⁵ = 261431629 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261431663) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 45591 + ... + 51003.

It is an arithmetic number, because the mean of its divisors is an integer number (23096124).

Almost surely, 2^261431661 is an apocalyptic number.

It is an amenable number.

261431661 is a deficient number, since it is larger than the sum of its proper divisors (108106323).

261431661 is a wasteful number, since it uses less digits than its factorization.

261431661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6380.

The product of its digits is 5184, while the sum is 30.

The square root of 261431661 is about 16168.8484747678. The cubic root of 261431661 is about 639.4197711569.

The spelling of 261431661 in words is "two hundred sixty-one million, four hundred thirty-one thousand, six hundred sixty-one".