665690 has 8 divisors (see below), whose sum is σ = 1198260. Its totient is φ = 266272.

The previous prime is 665677. The next prime is 665713. The reversal of 665690 is 96566.

It can be written as a sum of positive squares in 2 ways, for example, as 582169 + 83521 = 763^2 + 289^2 .

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

It is a super-2 number, since 2×665690² = 886286352200, which contains 22 as substring.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 33275 + ... + 33294.

2⁶⁶⁵⁶⁹⁰ is an apocalyptic number.

665690 is a deficient number, since it is larger than the sum of its proper divisors (532570).

665690 is a wasteful number, since it uses less digits than its factorization.

665690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66576.

The product of its (nonzero) digits is 9720, while the sum is 32.

The square root of 665690 is about 815.8982779734. The cubic root of 665690 is about 87.3153657784.

The spelling of 665690 in words is "six hundred sixty-five thousand, six hundred ninety".