261856073861 has 4 divisors (see below), whose sum is σ = 261857628300. Its totient is φ = 261854519424.

The previous prime is 261856073851. The next prime is 261856073863. The reversal of 261856073861 is 168370658162.

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

It can be written as a sum of positive squares in 2 ways, for example, as 167011168900 + 94844904961 = 408670^2 + 307969^2 .

It is a cyclic number.

It is not a de Polignac number, because 261856073861 - 2⁶ = 261856073797 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261856073863) 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, 488876 + ... + 873333.

It is an arithmetic number, because the mean of its divisors is an integer number (65464407075).

Almost surely, 2^261856073861 is an apocalyptic number.

It is an amenable number.

261856073861 is a deficient number, since it is larger than the sum of its proper divisors (1554439).

261856073861 is a wasteful number, since it uses less digits than its factorization.

261856073861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1554438.

The product of its (nonzero) digits is 2903040, while the sum is 53.

The spelling of 261856073861 in words is "two hundred sixty-one billion, eight hundred fifty-six million, seventy-three thousand, eight hundred sixty-one".