2111661 has 6 divisors (see below), whose sum is σ = 3050190. Its totient is φ = 1407768.

The previous prime is 2111633. The next prime is 2111677. The reversal of 2111661 is 1661112.

2111661 is a `hidden beast` number, since 2 + 1 + 1 + 1 + 661 = 666.

It can be written as a sum of positive squares in only one way, i.e., 1664100 + 447561 = 1290^2 + 669^2 .

It is not a de Polignac number, because 2111661 - 2⁶ = 2111597 is a prime.

It is a super-2 number, since 2×2111661² = 8918224357842, which contains 22 as substring.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2111861) 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, 117306 + ... + 117323.

It is an arithmetic number, because the mean of its divisors is an integer number (508365).

2^2111661 is an apocalyptic number.

It is an amenable number.

2111661 is a deficient number, since it is larger than the sum of its proper divisors (938529).

2111661 is a wasteful number, since it uses less digits than its factorization.

2111661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 234635 (or 234632 counting only the distinct ones).

The product of its digits is 72, while the sum is 18.

The square root of 2111661 is about 1453.1555319373. The cubic root of 2111661 is about 128.2945082231.

Adding to 2111661 its reverse (1661112), we get a palindrome (3772773).

It can be divided in two parts, 2111 and 661, that added together give a palindrome (2772).

The spelling of 2111661 in words is "two million, one hundred eleven thousand, six hundred sixty-one".