261856496861 has 4 divisors (see below), whose sum is σ = 261875200224. Its totient is φ = 261837793500.

The previous prime is 261856496857. The next prime is 261856496887. The reversal of 261856496861 is 168694658162.

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 261856496861 - 2² = 261856496857 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 261856496794 and 261856496803.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261856496801) 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, 9330665 + ... + 9358686.

It is an arithmetic number, because the mean of its divisors is an integer number (65468800056).

Almost surely, 2^261856496861 is an apocalyptic number.

It is an amenable number.

261856496861 is a deficient number, since it is larger than the sum of its proper divisors (18703363).

261856496861 is a wasteful number, since it uses less digits than its factorization.

261856496861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18703362.

The product of its digits is 29859840, while the sum is 62.

The spelling of 261856496861 in words is "two hundred sixty-one billion, eight hundred fifty-six million, four hundred ninety-six thousand, eight hundred sixty-one".