665440 has 24 divisors (see below), whose sum is σ = 1572480. Its totient is φ = 266112.

The previous prime is 665429. The next prime is 665447. The reversal of 665440 is 44566.

It is a happy number.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665447) 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, 1920 + ... + 2239.

It is an arithmetic number, because the mean of its divisors is an integer number (65520).

2⁶⁶⁵⁴⁴⁰ is an apocalyptic number.

It is an amenable number.

665440 is an abundant number, since it is smaller than the sum of its proper divisors (907040).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

665440 is a wasteful number, since it uses less digits than its factorization.

665440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4174 (or 4166 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 25.

The square root of 665440 is about 815.7450582137. The cubic root of 665440 is about 87.3044339760.

The spelling of 665440 in words is "six hundred sixty-five thousand, four hundred forty".