2021605 has 4 divisors (see below), whose sum is σ = 2425932. Its totient is φ = 1617280.

The previous prime is 2021599. The next prime is 2021609. The reversal of 2021605 is 5061202.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 231361 + 1790244 = 481^2 + 1338^2 .

It is not a de Polignac number, because 2021605 - 2³ = 2021597 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2021609) 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 3 ways as a sum of consecutive naturals, for example, 202156 + ... + 202165.

It is an arithmetic number, because the mean of its divisors is an integer number (606483).

2^2021605 is an apocalyptic number.

It is an amenable number.

2021605 is a deficient number, since it is larger than the sum of its proper divisors (404327).

2021605 is an equidigital number, since it uses as much as digits as its factorization.

2021605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 404326.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 2021605 is about 1421.8315652707. The cubic root of 2021605 is about 126.4441576811. Note that the first 3 decimals are identical.

Adding to 2021605 its reverse (5061202), we get a palindrome (7082807).

The spelling of 2021605 in words is "two million, twenty-one thousand, six hundred five".