2166021 has 60 divisors (see below), whose sum is σ = 4055436. Its totient is φ = 1140480.

The previous prime is 2166007. The next prime is 2166023. The reversal of 2166021 is 1206612.

It is a happy number.

2166021 is a `hidden beast` number, since 2 + 1 + 660 + 2 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 980100 + 1185921 = 990^2 + 1089^2 .

It is not a de Polignac number, because 2166021 - 2⁶ = 2165957 is a prime.

It is a Curzon number.

It is a zygodrome in base 12.

It is a junction number, because it is equal to n+sod(n) for n = 2165985 and 2166003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2166023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 127405 + ... + 127421.

2^2166021 is an apocalyptic number.

It is an amenable number.

2166021 is a deficient number, since it is larger than the sum of its proper divisors (1889415).

2166021 is a wasteful number, since it uses less digits than its factorization.

2166021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64 (or 44 counting only the distinct ones).

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

The square root of 2166021 is about 1471.7408059845. The cubic root of 2166021 is about 129.3860797064.

The spelling of 2166021 in words is "two million, one hundred sixty-six thousand, twenty-one".