261211112161 has 4 divisors (see below), whose sum is σ = 267285789232. Its totient is φ = 255136435092.

The previous prime is 261211112147. The next prime is 261211112189. The reversal of 261211112161 is 161211112162.

It is a happy number.

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 261211112161 - 2²⁷ = 261076894433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261211112131) 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, 3037338471 + ... + 3037338556.

It is an arithmetic number, because the mean of its divisors is an integer number (66821447308).

Almost surely, 2^261211112161 is an apocalyptic number.

It is an amenable number.

261211112161 is a deficient number, since it is larger than the sum of its proper divisors (6074677071).

261211112161 is an equidigital number, since it uses as much as digits as its factorization.

261211112161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6074677070.

The product of its digits is 288, while the sum is 25.

Subtracting from 261211112161 its reverse (161211112162), we obtain a palindrome (99999999999).

The spelling of 261211112161 in words is "two hundred sixty-one billion, two hundred eleven million, one hundred twelve thousand, one hundred sixty-one".