2101681 has 2 divisors, whose sum is σ = 2101682. Its totient is φ = 2101680.

The previous prime is 2101669. The next prime is 2101703. The reversal of 2101681 is 1861012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1461681 + 640000 = 1209^2 + 800^2 .

It is a cyclic number.

It is not a de Polignac number, because 2101681 - 2⁷ = 2101553 is a prime.

It is a super-2 number, since 2×2101681² = 8834126051522, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (2101621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1050840 + 1050841.

It is an arithmetic number, because the mean of its divisors is an integer number (1050841).

2^2101681 is an apocalyptic number.

It is an amenable number.

2101681 is a deficient number, since it is larger than the sum of its proper divisors (1).

2101681 is an equidigital number, since it uses as much as digits as its factorization.

2101681 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 96, while the sum is 19.

The square root of 2101681 is about 1449.7175586989. The cubic root of 2101681 is about 128.0920764900.

Adding to 2101681 its reverse (1861012), we get a palindrome (3962693).

It can be divided in two parts, 210 and 1681, that added together give a triangular number (1891 = T₆₁).

The spelling of 2101681 in words is "two million, one hundred one thousand, six hundred eighty-one".