665980 has 48 divisors (see below), whose sum is σ = 1645056. Its totient is φ = 221760.

The previous prime is 665953. The next prime is 665981. The reversal of 665980 is 89566.

665980 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665981) by changing a digit.

665980 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9345 + ... + 9415.

It is an arithmetic number, because the mean of its divisors is an integer number (34272).

2⁶⁶⁵⁹⁸⁰ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 665980, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (822528).

665980 is an abundant number, since it is smaller than the sum of its proper divisors (979076).

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

665980 is a wasteful number, since it uses less digits than its factorization.

665980 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 154 (or 152 counting only the distinct ones).

The product of its (nonzero) digits is 12960, while the sum is 34.

The square root of 665980 is about 816.0759768551. The cubic root of 665980 is about 87.3280432409.

The spelling of 665980 in words is "six hundred sixty-five thousand, nine hundred eighty".