665945 has 16 divisors (see below), whose sum is σ = 933120. Its totient is φ = 446784.

The previous prime is 665923. The next prime is 665947. The reversal of 665945 is 549566.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 665945 - 2¹² = 661849 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (35).

665945 is a modest number, since divided by 945 gives 665 as remainder.

It is a plaindrome in base 9.

It is not an unprimeable number, because it can be changed into a prime (665947) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1676 + ... + 2034.

It is an arithmetic number, because the mean of its divisors is an integer number (58320).

2⁶⁶⁵⁹⁴⁵ is an apocalyptic number.

It is an amenable number.

665945 is a deficient number, since it is larger than the sum of its proper divisors (267175).

665945 is a wasteful number, since it uses less digits than its factorization.

665945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 424.

The product of its digits is 32400, while the sum is 35.

The square root of 665945 is about 816.0545324915. The cubic root of 665945 is about 87.3265133976.

The spelling of 665945 in words is "six hundred sixty-five thousand, nine hundred forty-five".