2181621 has 16 divisors (see below), whose sum is σ = 3160640. Its totient is φ = 1338480.

The previous prime is 2181611. The next prime is 2181629. The reversal of 2181621 is 1261812.

2181621 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 2181621 - 2¹⁴ = 2165237 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2181629) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6426 + ... + 6756.

It is an arithmetic number, because the mean of its divisors is an integer number (197540).

2^2181621 is an apocalyptic number.

It is an amenable number.

2181621 is a deficient number, since it is larger than the sum of its proper divisors (979019).

2181621 is an equidigital number, since it uses as much as digits as its factorization.

2181621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 373 (or 347 counting only the distinct ones).

The product of its digits is 192, while the sum is 21.

The square root of 2181621 is about 1477.0311438829. The cubic root of 2181621 is about 129.6959561235.

The spelling of 2181621 in words is "two million, one hundred eighty-one thousand, six hundred twenty-one".