261121121161 has 4 divisors (see below), whose sum is σ = 262474080532. Its totient is φ = 259768161792.

The previous prime is 261121121077. The next prime is 261121121207. The reversal of 261121121161 is 161121121162.

It is a happy number.

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 29706246025 + 231414875136 = 172355^2 + 481056^2 .

It is a cyclic number.

It is not a de Polignac number, because 261121121161 - 2⁷ = 261121121033 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261121121561) 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, 676479396 + ... + 676479781.

It is an arithmetic number, because the mean of its divisors is an integer number (65618520133).

Almost surely, 2^261121121161 is an apocalyptic number.

It is an amenable number.

261121121161 is a deficient number, since it is larger than the sum of its proper divisors (1352959371).

261121121161 is a wasteful number, since it uses less digits than its factorization.

261121121161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1352959370.

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

Subtracting from 261121121161 its reverse (161121121162), we obtain a palindrome (99999999999).

The spelling of 261121121161 in words is "two hundred sixty-one billion, one hundred twenty-one million, one hundred twenty-one thousand, one hundred sixty-one".