2186721 has 12 divisors (see below), whose sum is σ = 3175380. Its totient is φ = 1450080.

The previous prime is 2186719. The next prime is 2186731. The reversal of 2186721 is 1276812.

2186721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 1782225 + 404496 = 1335^2 + 636^2 .

It is not a de Polignac number, because 2186721 - 2¹ = 2186719 is a prime.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (2186731) 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 11 ways as a sum of consecutive naturals, for example, 1531 + ... + 2591.

It is an arithmetic number, because the mean of its divisors is an integer number (264615).

2^2186721 is an apocalyptic number.

It is an amenable number.

2186721 is a deficient number, since it is larger than the sum of its proper divisors (988659).

2186721 is a wasteful number, since it uses less digits than its factorization.

2186721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1296 (or 1293 counting only the distinct ones).

The product of its digits is 1344, while the sum is 27.

The square root of 2186721 is about 1478.7565722593. The cubic root of 2186721 is about 129.7969413724.

Subtracting from 2186721 its reverse (1276812), we obtain a palindrome (909909).

The spelling of 2186721 in words is "two million, one hundred eighty-six thousand, seven hundred twenty-one".