261556385 has 4 divisors (see below), whose sum is σ = 313867668. Its totient is φ = 209245104.

The previous prime is 261556327. The next prime is 261556387. The reversal of 261556385 is 583655162.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 96510976 + 165045409 = 9824^2 + 12847^2 .

It is a cyclic number.

It is not a de Polignac number, because 261556385 - 2¹⁰ = 261555361 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261556387) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26155634 + ... + 26155643.

It is an arithmetic number, because the mean of its divisors is an integer number (78466917).

Almost surely, 2^261556385 is an apocalyptic number.

It is an amenable number.

261556385 is a deficient number, since it is larger than the sum of its proper divisors (52311283).

261556385 is an equidigital number, since it uses as much as digits as its factorization.

261556385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52311282.

The product of its digits is 216000, while the sum is 41.

The square root of 261556385 is about 16172.7049376411. The cubic root of 261556385 is about 639.5214399347.

The spelling of 261556385 in words is "two hundred sixty-one million, five hundred fifty-six thousand, three hundred eighty-five".