261491507583 has 4 divisors (see below), whose sum is σ = 348655343448. Its totient is φ = 174327671720.

The previous prime is 261491507581. The next prime is 261491507597. The reversal of 261491507583 is 385705194162.

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

It is a cyclic number.

It is not a de Polignac number, because 261491507583 - 2¹ = 261491507581 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261491507581) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 43581917928 + ... + 43581917933.

It is an arithmetic number, because the mean of its divisors is an integer number (87163835862).

It is a 1-persistent number, because it is pandigital, but 2⋅261491507583 = 522983015166 is not.

Almost surely, 2^261491507583 is an apocalyptic number.

261491507583 is a deficient number, since it is larger than the sum of its proper divisors (87163835865).

261491507583 is an equidigital number, since it uses as much as digits as its factorization.

261491507583 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87163835864.

The product of its (nonzero) digits is 1814400, while the sum is 51.

The spelling of 261491507583 in words is "two hundred sixty-one billion, four hundred ninety-one million, five hundred seven thousand, five hundred eighty-three".