1666591 has 8 divisors (see below), whose sum is σ = 1768064. Its totient is φ = 1568160.

The previous prime is 1666589. The next prime is 1666597. The reversal of 1666591 is 1956661.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1666591 - 2¹ = 1666589 is a prime.

It is a super-2 number, since 2×1666591² = 5555051122562, 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 (1666597) 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 7 ways as a sum of consecutive naturals, for example, 421 + ... + 1873.

It is an arithmetic number, because the mean of its divisors is an integer number (221008).

2^1666591 is an apocalyptic number.

1666591 is a deficient number, since it is larger than the sum of its proper divisors (101473).

1666591 is a wasteful number, since it uses less digits than its factorization.

1666591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1521.

The product of its digits is 9720, while the sum is 34.

The square root of 1666591 is about 1290.9651428292. The cubic root of 1666591 is about 118.5613158674.

The spelling of 1666591 in words is "one million, six hundred sixty-six thousand, five hundred ninety-one".