261581257 has 6 divisors (see below), whose sum is σ = 304288458. Its totient is φ = 224212464.

The previous prime is 261581239. The next prime is 261581263. The reversal of 261581257 is 752185162.

It can be written as a sum of positive squares in only one way, i.e., 254051721 + 7529536 = 15939^2 + 2744^2 .

It is not a de Polignac number, because 261581257 - 2²⁷ = 127363529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261581297) 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 5 ways as a sum of consecutive naturals, for example, 2669148 + ... + 2669245.

It is an arithmetic number, because the mean of its divisors is an integer number (50714743).

Almost surely, 2^261581257 is an apocalyptic number.

It is an amenable number.

261581257 is a deficient number, since it is larger than the sum of its proper divisors (42707201).

261581257 is an equidigital number, since it uses as much as digits as its factorization.

261581257 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5338407 (or 5338400 counting only the distinct ones).

The product of its digits is 33600, while the sum is 37.

The square root of 261581257 is about 16173.4738692713. The cubic root of 261581257 is about 639.5417104818.

The spelling of 261581257 in words is "two hundred sixty-one million, five hundred eighty-one thousand, two hundred fifty-seven".