2021661 has 6 divisors (see below), whose sum is σ = 2920190. Its totient is φ = 1347768.

The previous prime is 2021659. The next prime is 2021671. The reversal of 2021661 is 1661202.

It is a happy number.

2021661 is a `hidden beast` number, since 2 + 0 + 2 + 1 + 661 = 666.

It can be written as a sum of positive squares in only one way, i.e., 2013561 + 8100 = 1419^2 + 90^2 .

It is not a de Polignac number, because 2021661 - 2¹ = 2021659 is a prime.

It is a super-2 number, since 2×2021661² = 8174226397842, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2021651) 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 5 ways as a sum of consecutive naturals, for example, 112306 + ... + 112323.

2^2021661 is an apocalyptic number.

It is an amenable number.

2021661 is a deficient number, since it is larger than the sum of its proper divisors (898529).

2021661 is a wasteful number, since it uses less digits than its factorization.

2021661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 224635 (or 224632 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

The square root of 2021661 is about 1421.8512580435. The cubic root of 2021661 is about 126.4453252035.

Adding to 2021661 its reverse (1661202), we get a palindrome (3682863).

The spelling of 2021661 in words is "two million, twenty-one thousand, six hundred sixty-one".