665657 has 4 divisors (see below), whose sum is σ = 669300. Its totient is φ = 662016.

The previous prime is 665633. The next prime is 665659. The reversal of 665657 is 756566.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 756566 = 2 ⋅378283.

It can be written as a sum of positive squares in 2 ways, for example, as 55696 + 609961 = 236^2 + 781^2 .

It is a cyclic number.

It is not a de Polignac number, because 665657 - 2¹⁰ = 664633 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (665659) 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, 1532 + ... + 1917.

It is an arithmetic number, because the mean of its divisors is an integer number (167325).

2⁶⁶⁵⁶⁵⁷ is an apocalyptic number.

It is an amenable number.

665657 is a deficient number, since it is larger than the sum of its proper divisors (3643).

665657 is a wasteful number, since it uses less digits than its factorization.

665657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3642.

The product of its digits is 37800, while the sum is 35.

The square root of 665657 is about 815.8780546136. The cubic root of 665657 is about 87.3139229373.

Subtracting 665657 from its reverse (756566), we obtain a palindrome (90909).

The spelling of 665657 in words is "six hundred sixty-five thousand, six hundred fifty-seven".