1666289 has 4 divisors (see below), whose sum is σ = 1764324. Its totient is φ = 1568256.

The previous prime is 1666279. The next prime is 1666297. The reversal of 1666289 is 9826661.

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 1459264 + 207025 = 1208^2 + 455^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1666289 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1666279) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 48992 + ... + 49025.

It is an arithmetic number, because the mean of its divisors is an integer number (441081).

2^1666289 is an apocalyptic number.

It is an amenable number.

1666289 is a deficient number, since it is larger than the sum of its proper divisors (98035).

1666289 is an equidigital number, since it uses as much as digits as its factorization.

1666289 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 98034.

The product of its digits is 31104, while the sum is 38.

The square root of 1666289 is about 1290.8481707776. The cubic root of 1666289 is about 118.5541540062.

The spelling of 1666289 in words is "one million, six hundred sixty-six thousand, two hundred eighty-nine".