261661166161 has 8 divisors (see below), whose sum is σ = 264286264320. Its totient is φ = 259044892848.

The previous prime is 261661166153. The next prime is 261661166203. The reversal of 261661166161 is 161661166162.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 261661166161 - 2³ = 261661166153 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261661160161) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2146606 + ... + 2265223.

It is an arithmetic number, because the mean of its divisors is an integer number (33035783040).

Almost surely, 2^261661166161 is an apocalyptic number.

It is an amenable number.

261661166161 is a deficient number, since it is larger than the sum of its proper divisors (2625098159).

261661166161 is a wasteful number, since it uses less digits than its factorization.

261661166161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4412423.

The product of its digits is 93312, while the sum is 43.

Subtracting from 261661166161 its reverse (161661166162), we obtain a palindrome (99999999999).

The spelling of 261661166161 in words is "two hundred sixty-one billion, six hundred sixty-one million, one hundred sixty-six thousand, one hundred sixty-one".