2161111681 has 4 divisors (see below), whose sum is σ = 2213821764. Its totient is φ = 2108401600.

The previous prime is 2161111669. The next prime is 2161111727. The reversal of 2161111681 is 1861111612.

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 1139670081 + 1021441600 = 33759^2 + 31960^2 .

It is a cyclic number.

It is not a de Polignac number, because 2161111681 - 2¹¹ = 2161109633 is a prime.

It is a super-2 number, since 2×2161111681² = 9340807395509291522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2161111081) 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, 26354980 + ... + 26355061.

It is an arithmetic number, because the mean of its divisors is an integer number (553455441).

Almost surely, 2^2161111681 is an apocalyptic number.

It is an amenable number.

2161111681 is a deficient number, since it is larger than the sum of its proper divisors (52710083).

2161111681 is an equidigital number, since it uses as much as digits as its factorization.

2161111681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52710082.

The product of its digits is 576, while the sum is 28.

The square root of 2161111681 is about 46487.7583993894. The cubic root of 2161111681 is about 1292.8825393288.

The spelling of 2161111681 in words is "two billion, one hundred sixty-one million, one hundred eleven thousand, six hundred eighty-one".