3666581 has 2 divisors, whose sum is σ = 3666582. Its totient is φ = 3666580.

The previous prime is 3666539. The next prime is 3666583. The reversal of 3666581 is 1856663.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 3478225 + 188356 = 1865^2 + 434^2 .

It is a cyclic number.

It is not a de Polignac number, because 3666581 - 2¹⁴ = 3650197 is a prime.

It is a super-2 number, since 2×3666581² = 26887632459122, which contains 22 as substring.

Together with 3666583, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (3666583) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1833290 + 1833291.

It is an arithmetic number, because the mean of its divisors is an integer number (1833291).

Almost surely, 2^3666581 is an apocalyptic number.

It is an amenable number.

3666581 is a deficient number, since it is larger than the sum of its proper divisors (1).

3666581 is an equidigital number, since it uses as much as digits as its factorization.

3666581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 25920, while the sum is 35.

The square root of 3666581 is about 1914.8318464032. The cubic root of 3666581 is about 154.2009660556.

The spelling of 3666581 in words is "three million, six hundred sixty-six thousand, five hundred eighty-one".