261603565 has 8 divisors (see below), whose sum is σ = 332390520. Its totient is φ = 196972032.

The previous prime is 261603557. The next prime is 261603569. The reversal of 261603565 is 565306162.

It can be written as a sum of positive squares in 4 ways, for example, as 97199881 + 164403684 = 9859^2 + 12822^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 261603565 - 2³ = 261603557 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 261603565.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261603569) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1538760 + ... + 1538929.

It is an arithmetic number, because the mean of its divisors is an integer number (41548815).

Almost surely, 2^261603565 is an apocalyptic number.

It is an amenable number.

261603565 is a deficient number, since it is larger than the sum of its proper divisors (70786955).

261603565 is a wasteful number, since it uses less digits than its factorization.

261603565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3077711.

The product of its (nonzero) digits is 32400, while the sum is 34.

The square root of 261603565 is about 16174.1635023268. The cubic root of 261603565 is about 639.5598902896.

The spelling of 261603565 in words is "two hundred sixty-one million, six hundred three thousand, five hundred sixty-five".