261099538441 has 9 divisors (see below), whose sum is σ = 303732195399. Its totient is φ = 223796538504.

The previous prime is 261099538363. The next prime is 261099538457. The reversal of 261099538441 is 144835990162.

The square root of 261099538441 is 510979.

It is a perfect power (a square), and thus also a powerful number.

261099538441 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 83356351225 + 177743187216 = 288715^2 + 421596^2 .

It is not a de Polignac number, because 261099538441 - 2¹⁷ = 261099407369 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261099538241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 3540355 + ... + 3613351.

It is an arithmetic number, because the mean of its divisors is an integer number (33748021711).

Almost surely, 2^261099538441 is an apocalyptic number.

261099538441 is the 510979-th square number.

261099538441 is the 255490-th centered octagonal number.

It is an amenable number.

261099538441 is a deficient number, since it is larger than the sum of its proper divisors (42632656958).

261099538441 is an frugal number, since it uses more digits than its factorization.

261099538441 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 146008 (or 73004 counting only the distinct ones).

The product of its (nonzero) digits is 1866240, while the sum is 52.

The spelling of 261099538441 in words is "two hundred sixty-one billion, ninety-nine million, five hundred thirty-eight thousand, four hundred forty-one".