2161378761 has 4 divisors (see below), whose sum is σ = 2881838352. Its totient is φ = 1440919172.

The previous prime is 2161378757. The next prime is 2161378783. The reversal of 2161378761 is 1678731612.

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 2161378761 - 2² = 2161378757 is a prime.

It is not an unprimeable number, because it can be changed into a prime (2161378061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 360229791 + ... + 360229796.

It is an arithmetic number, because the mean of its divisors is an integer number (720459588).

Almost surely, 2^2161378761 is an apocalyptic number.

It is an amenable number.

2161378761 is a deficient number, since it is larger than the sum of its proper divisors (720459591).

2161378761 is an equidigital number, since it uses as much as digits as its factorization.

2161378761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 720459590.

The product of its digits is 84672, while the sum is 42.

The square root of 2161378761 is about 46490.6308948373. The cubic root of 2161378761 is about 1292.9357972343.

The spelling of 2161378761 in words is "two billion, one hundred sixty-one million, three hundred seventy-eight thousand, seven hundred sixty-one".