261204561 has 16 divisors (see below), whose sum is σ = 387868800. Its totient is φ = 173731824.

The previous prime is 261204551. The next prime is 261204641. The reversal of 261204561 is 165402162.

261204561 is a `hidden beast` number, since 2 + 612 + 0 + 45 + 6 + 1 = 666.

261204561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 261204561 - 2⁵ = 261204529 is a prime.

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

It is not an unprimeable number, because it can be changed into a prime (261204551) 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, 835 + ... + 22871.

It is an arithmetic number, because the mean of its divisors is an integer number (24241800).

Almost surely, 2^261204561 is an apocalyptic number.

It is an amenable number.

261204561 is a deficient number, since it is larger than the sum of its proper divisors (126664239).

261204561 is a wasteful number, since it uses less digits than its factorization.

261204561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22485 (or 22479 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 27.

The square root of 261204561 is about 16161.8241854068. The cubic root of 261204561 is about 639.2345675013.

The spelling of 261204561 in words is "two hundred sixty-one million, two hundred four thousand, five hundred sixty-one".