261381609 has 12 divisors (see below), whose sum is σ = 377707252. Its totient is φ = 174182400.

The previous prime is 261381599. The next prime is 261381629. The reversal of 261381609 is 906183162.

It can be written as a sum of positive squares in 2 ways, for example, as 85155984 + 176225625 = 9228^2 + 13275^2 .

It is not a de Polignac number, because 261381609 - 2⁷ = 261381481 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261381629) 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 11 ways as a sum of consecutive naturals, for example, 25929 + ... + 34569.

Almost surely, 2^261381609 is an apocalyptic number.

It is an amenable number.

261381609 is a deficient number, since it is larger than the sum of its proper divisors (116325643).

261381609 is a wasteful number, since it uses less digits than its factorization.

261381609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12008 (or 12005 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 36.

The square root of 261381609 is about 16167.3006095637. The cubic root of 261381609 is about 639.3789621733.

The spelling of 261381609 in words is "two hundred sixty-one million, three hundred eighty-one thousand, six hundred nine".