2161611261 has 12 divisors (see below), whose sum is σ = 3175248960. Its totient is φ = 1416648840.

The previous prime is 2161611241. The next prime is 2161611269. The reversal of 2161611261 is 1621161612.

2161611261 is a `hidden beast` number, since 21 + 6 + 1 + 611 + 26 + 1 = 666.

It is not a de Polignac number, because 2161611261 - 2⁶ = 2161611197 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2161611269) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2034885 + ... + 2035946.

It is an arithmetic number, because the mean of its divisors is an integer number (264604080).

Almost surely, 2^2161611261 is an apocalyptic number.

It is an amenable number.

2161611261 is a deficient number, since it is larger than the sum of its proper divisors (1013637699).

2161611261 is a wasteful number, since it uses less digits than its factorization.

2161611261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4070896 (or 4070893 counting only the distinct ones).

The product of its digits is 864, while the sum is 27.

The square root of 2161611261 is about 46493.1313314128. The cubic root of 2161611261 is about 1292.9821560370.

Adding to 2161611261 its reverse (1621161612), we get a palindrome (3782772873).

The spelling of 2161611261 in words is "two billion, one hundred sixty-one million, six hundred eleven thousand, two hundred sixty-one".