2166581 has 2 divisors, whose sum is σ = 2166582. Its totient is φ = 2166580.

The previous prime is 2166557. The next prime is 2166601. The reversal of 2166581 is 1856612.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1136356 + 1030225 = 1066^2 + 1015^2 .

It is a cyclic number.

It is not a de Polignac number, because 2166581 - 2¹⁰ = 2165557 is a prime.

It is a super-2 number, since 2×2166581² = 9388146459122, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2166511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1083290 + 1083291.

It is an arithmetic number, because the mean of its divisors is an integer number (1083291).

2^2166581 is an apocalyptic number.

It is an amenable number.

2166581 is a deficient number, since it is larger than the sum of its proper divisors (1).

2166581 is an equidigital number, since it uses as much as digits as its factorization.

2166581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2880, while the sum is 29.

The square root of 2166581 is about 1471.9310445806. The cubic root of 2166581 is about 129.3972291769.

The spelling of 2166581 in words is "two million, one hundred sixty-six thousand, five hundred eighty-one".