261771065 has 16 divisors (see below), whose sum is σ = 319280400. Its totient is φ = 205996032.

The previous prime is 261771061. The next prime is 261771089. The reversal of 261771065 is 560177162.

It can be written as a sum of positive squares in 8 ways, for example, as 10738729 + 251032336 = 3277^2 + 15844^2 .

It is a cyclic number.

It is not a de Polignac number, because 261771065 - 2² = 261771061 is a prime.

It is not an unprimeable number, because it can be changed into a prime (261771061) 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 15 ways as a sum of consecutive naturals, for example, 185081 + ... + 186489.

It is an arithmetic number, because the mean of its divisors is an integer number (19955025).

Almost surely, 2^261771065 is an apocalyptic number.

It is an amenable number.

261771065 is a deficient number, since it is larger than the sum of its proper divisors (57509335).

261771065 is a wasteful number, since it uses less digits than its factorization.

261771065 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1996.

The product of its (nonzero) digits is 17640, while the sum is 35.

The square root of 261771065 is about 16179.3406849599. The cubic root of 261771065 is about 639.6963606853.

The spelling of 261771065 in words is "two hundred sixty-one million, seven hundred seventy-one thousand, sixty-five".