2021561 has 4 divisors (see below), whose sum is σ = 2091300. Its totient is φ = 1951824.

The previous prime is 2021549. The next prime is 2021563. The reversal of 2021561 is 1651202.

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 383161 + 1638400 = 619^2 + 1280^2 .

It is a cyclic number.

It is not a de Polignac number, because 2021561 - 2⁶ = 2021497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2021563) 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, 34826 + ... + 34883.

It is an arithmetic number, because the mean of its divisors is an integer number (522825).

2^2021561 is an apocalyptic number.

It is an amenable number.

2021561 is a deficient number, since it is larger than the sum of its proper divisors (69739).

2021561 is an equidigital number, since it uses as much as digits as its factorization.

2021561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 69738.

The product of its (nonzero) digits is 120, while the sum is 17.

The square root of 2021561 is about 1421.8160921863. The cubic root of 2021561 is about 126.4432403269.

Adding to 2021561 its reverse (1651202), we get a palindrome (3672763).

The spelling of 2021561 in words is "two million, twenty-one thousand, five hundred sixty-one".