2161881 has 6 divisors (see below), whose sum is σ = 3122730. Its totient is φ = 1441248.

The previous prime is 2161871. The next prime is 2161883. The reversal of 2161881 is 1881612.

It can be written as a sum of positive squares in only one way, i.e., 1121481 + 1040400 = 1059^2 + 1020^2 .

It is not a de Polignac number, because 2161881 - 2⁵ = 2161849 is a prime.

It is a super-2 number, since 2×2161881² = 9347458916322, which contains 22 as substring.

It is an Ulam number.

It is not an unprimeable number, because it can be changed into a prime (2161883) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 120096 + ... + 120113.

It is an arithmetic number, because the mean of its divisors is an integer number (520455).

2^2161881 is an apocalyptic number.

It is an amenable number.

2161881 is a deficient number, since it is larger than the sum of its proper divisors (960849).

2161881 is a wasteful number, since it uses less digits than its factorization.

2161881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 240215 (or 240212 counting only the distinct ones).

The product of its digits is 768, while the sum is 27.

The square root of 2161881 is about 1470.3336356079. Note that the first 3 decimals coincide. The cubic root of 2161881 is about 129.3035935859.

The spelling of 2161881 in words is "two million, one hundred sixty-one thousand, eight hundred eighty-one".