665880 has 64 divisors (see below), whose sum is σ = 2073600. Its totient is φ = 170880.

The previous prime is 665857. The next prime is 665897. The reversal of 665880 is 88566.

It is a congruent number.

It is an unprimeable number.

665880 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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 15 ways as a sum of consecutive naturals, for example, 3631 + ... + 3809.

It is an arithmetic number, because the mean of its divisors is an integer number (32400).

2⁶⁶⁵⁸⁸⁰ is an apocalyptic number.

665880 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 665880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1036800).

665880 is an abundant number, since it is smaller than the sum of its proper divisors (1407720).

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

665880 is a wasteful number, since it uses less digits than its factorization.

665880 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 224 (or 220 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 33.

The square root of 665880 is about 816.0147057498. The cubic root of 665880 is about 87.3236721179.

The spelling of 665880 in words is "six hundred sixty-five thousand, eight hundred eighty".