261181565 has 8 divisors (see below), whose sum is σ = 318556248. Its totient is φ = 205519680.

The previous prime is 261181561. The next prime is 261181567. The reversal of 261181565 is 565181162.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 1907161 + 259274404 = 1381^2 + 16102^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 261181565 - 2² = 261181561 is a prime.

It is a Duffinian number.

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 7 ways as a sum of consecutive naturals, for example, 427862 + ... + 428471.

It is an arithmetic number, because the mean of its divisors is an integer number (39819531).

Almost surely, 2^261181565 is an apocalyptic number.

It is an amenable number.

261181565 is a deficient number, since it is larger than the sum of its proper divisors (57374683).

261181565 is an equidigital number, since it uses as much as digits as its factorization.

261181565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 856399.

The product of its digits is 14400, while the sum is 35.

The square root of 261181565 is about 16161.1127401550. The cubic root of 261181565 is about 639.2158079137.

The spelling of 261181565 in words is "two hundred sixty-one million, one hundred eighty-one thousand, five hundred sixty-five".