261891122849 has 4 divisors (see below), whose sum is σ = 263044828464. Its totient is φ = 260737417236.

The previous prime is 261891122821. The next prime is 261891122891. The reversal of 261891122849 is 948221198162.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 261891122849 - 2⁸ = 261891122593 is a prime.

It is a super-2 number, since 2×261891122849² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 261891122849.

It is not an unprimeable number, because it can be changed into a prime (261891122749) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 576852467 + ... + 576852920.

It is an arithmetic number, because the mean of its divisors is an integer number (65761207116).

Almost surely, 2^261891122849 is an apocalyptic number.

It is an amenable number.

261891122849 is a deficient number, since it is larger than the sum of its proper divisors (1153705615).

261891122849 is a wasteful number, since it uses less digits than its factorization.

261891122849 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1153705614.

The product of its digits is 995328, while the sum is 53.

The spelling of 261891122849 in words is "two hundred sixty-one billion, eight hundred ninety-one million, one hundred twenty-two thousand, eight hundred forty-nine".