665669 has 4 divisors (see below), whose sum is σ = 704844. Its totient is φ = 626496.

The previous prime is 665659. The next prime is 665677. The reversal of 665669 is 966566.

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 543169 + 122500 = 737^2 + 350^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-665669 is a prime.

It is a super-2 number, since 2×665669² = 886230435122, which contains 22 as substring.

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 (665629) 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 3 ways as a sum of consecutive naturals, for example, 19562 + ... + 19595.

It is an arithmetic number, because the mean of its divisors is an integer number (176211).

2⁶⁶⁵⁶⁶⁹ is an apocalyptic number.

It is an amenable number.

665669 is a deficient number, since it is larger than the sum of its proper divisors (39175).

665669 is a wasteful number, since it uses less digits than its factorization.

665669 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39174.

The product of its digits is 58320, while the sum is 38.

The square root of 665669 is about 815.8854086206. The cubic root of 665669 is about 87.3144476123.

The spelling of 665669 in words is "six hundred sixty-five thousand, six hundred sixty-nine".