2091681 has 6 divisors (see below), whose sum is σ = 3021330. Its totient is φ = 1394448.

The previous prime is 2091671. The next prime is 2091703. The reversal of 2091681 is 1861902.

It can be written as a sum of positive squares in only one way, i.e., 1742400 + 349281 = 1320^2 + 591^2 .

It is not a de Polignac number, because 2091681 - 2⁷ = 2091553 is a prime.

It is a super-2 number, since 2×2091681² = 8750258811522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (2091631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 116196 + ... + 116213.

It is an arithmetic number, because the mean of its divisors is an integer number (503555).

2^2091681 is an apocalyptic number.

It is an amenable number.

2091681 is a deficient number, since it is larger than the sum of its proper divisors (929649).

2091681 is a wasteful number, since it uses less digits than its factorization.

2091681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 232415 (or 232412 counting only the distinct ones).

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

The square root of 2091681 is about 1446.2644986309. The cubic root of 2091681 is about 127.8885952872. Note that the first 3 decimals are identical.

It can be divided in two parts, 2091 and 681, that added together give a palindrome (2772).

The spelling of 2091681 in words is "two million, ninety-one thousand, six hundred eighty-one".